What is the biblical basis that Jesus could not sin?

There is no biblical basis for this, but only man's tradition introduced by Catholic Church through the Gnostic or Manichaean influences in Augustine like leaders who shaped the doctrines that is even held by the reformers. First, they interpolated that man is totally depraved and unable to do any good, in order to rid the guilt consciousness & responsibility from sin. This gave birth to original sin (something unheard to the Jews), that all children of Adam are infected with the sin of Adam, making sin as a genetic disease and defect, yet Christ and his mother despite being children of Adam were to be exempt from that original sin. This basically distinguish Jesus with the rest of mankind, the motivation to make Jesus infallible, untouchable superhuman or demigod is similar to the Gnostic's denial of the incarnation to avoid his suffering and death deemed embarrassing to them. The traditionalists use the virgin birth as a scientific conjecture to postulate the exemption from the original sin disease, by arguing that it might only be passed on through males, and since Jesus had no male parent in his birth, he bypassed the original sin. This scientific conjecture does nothing but disregard his true humanity, making him a half human by saying he had no Y chromosome in his DNA.

To me, these doctrines (Catholics or Protestants) essentially deny the atonement of Christ by denying his humanity, just like the Gnostics did. The motivation behind such bizarre interpolations is to justify sin or lawlessness.

What is the biblical basis that Jesus could not sin?

In short, there is no biblical basis that Jesus could not sin.

So this begs the question, could Jesus sin?

2 Peter 2:4 shows us that angels can sin:

Certainly God did not refrain from punishing the angels who sinned

Hebrews 2:9 tells us Jesus status or condition while on earth:

But we do see Jesus, who was made a little lower than angels

So, yes, the possibility of Jesus sinning was there. But since he existed with Jehovah God for countless eons (Mic 5:2; Col 1:15; Rev 3:14), he learned what his Father required of him while here on earth to offer himself as a ransom sacrifice for all mankind. (Mark 4:45)

This is from a Jehovah's Witness perspective.

[All scripture quotations from the New World Translation of the Holy Scriptures (Study Edition)]

Maybe it is simple. Adam sinned all on his own, and brought death, mortality upon the whole human race. Romans 5 teaches this and also, when translated correctly, says we now, ever since Adam, sin because we are mortal. Paul teaches the problem is not so much that people sin, but that they are enslaved (beyond their will) to it. That is the power Jesus came to break.

So people sin because they are enslaved to sin, they cannot help but to sin until that power is broken. We are sealed with the Holy Spirit and that is what sanctifies us and breaks that dominion of sin over us. Now sin can reign only if we allow it to.

All that is to set up a comparison.

If mortality, death, is what causes people to sin, then remove the cause and the effect disappears. The life of Jesus came from God through the seed God implanted in Mary's womb. By the flesh, he's the Son of David through Mary, but his life is from God.

Perhaps the life Jesus had, not from Adam but from God, was instrumental in his sinlessness. Just thinking...

You are looking at the verse backwards and thinking exactly what it does not say. Jesus was tempted like we are tempted, meaning he had the physical capability to sin. "... one who in every respect has been tempted as we are" (Heb. 4:15, ESV) means when he was tempted he faced the decision whether to sin or not sin. Otherwise, he wasn't tempted as we are. He faced the decision, but that he did not sin. To do the will of the Father was Jesus' decision. Humanly he could have decided otherwise.

Do you think that I cannot appeal to my Father, and he will at once send me more than twelve legions of angels?  But how then should the Scriptures be fulfilled, that it must be so?” (Matt. 26:53–54, ESV)

Jesus could not sin because he decided not to sin as an attribute; just as it is impossible for God to lie, not because he is physically incapable, but because of his chosen attribute. Was temptation a farce when Jesus was sweating profusely as if bleeding facing the decision to die on the cross? I don't think so.

To my knowledge, there is no verse that states explicitly Jesus could sin or could not sin, however from scripture we can infer that He could not sin, since He is fully God (John 1: "the Word was God" and "the Word became flesh and dwelt among us"), but we need to define some terms first.

Firstly, what is sin? If we take sin to be willing something contrary to the Divine Will, it becomes clear that God is unable to sin. It is furthermore not a limitation on His power that He cannot sin, but a logical consequence of the definition of sin itself. Just as God cannot create a square circle owing to the definition (or in this case lack of a coherent definition) of a square circle itself, God cannot sin because to do so would be to do something contrary to His own will, which is of course impossible for an omnipotent being.

Now why does Jesus say "not my will, but Thine be done"? Here we need to distinguish between His natures. He is fully God and fully man. How this is possible is a mystery, but we know from the deposit of faith handed down tot he Church that Jesus is a single person with two natures: a divine and a human nature. His human nature thus has a human will, but He is a divine person. By subjugating his human appetitive will (the will that seeks bodily goods) to His divine will, He behaves in a manner fitting to the God-man. Jesus in His human will really does desire to avoid the pain of the cross - who would want to suffer that? But being a perfect man and God Himself, He gives over that human desire to the Father such that He makes His human body, and ultimately His human will, subject to the will of the Divine Essence.

Jesus, being God, cannot sin because to do so would be to rebel against His own will. Yet, being a person of dual natures, He has two wills, and one will must always be subjected to the other. His subjecting His human will to the Divine Will is a model for us: we are also called to subject our human wills to the will of God.

What is the biblical basis that Jesus could not sin?

First of all, some preliminary remarks from R. Carlton Wynne who is the assistant professor of systematic theology and apologetics at Westminster Theological Seminary in Glenside, Pennsylvania:

Scripture is clear that Jesus, the sinless Son of God, was tempted to sin (Matthew 4:1–11; Mark 1:13; Luke 4:2; 22:28; Hebrews 2:18).1 In addition, the author of the book of Hebrews assures Christians that it is because he was “tempted as we are” (Hebrews 4:15) that our ascended Savior is able to sympathize with our weaknesses as fallen people. However, the same verse adds that the tempted Christ was also “without sin.” That is, we Christians have a Savior who has shared our experience with temptation, but who, as the spotless Lamb of God, was perfectly suited to be our substitutionary sacrifice at Calvary and now lives as our High Priest in heaven. All who look for divine sympathy and relief from the persistently alluring hand of sin may be supremely comforted.

Upholding Both Natures in the Divine Son

One challenge related to Christ’s two natures is to preserve the integrity of Christ’s human will as it functions via the divine Son. This is especially true when advocates of the peccability and impeccability positions describe the volitional activity of the God-man. Both camps run the risk of reaching their conclusions by expanding one nature beyond its proper limit such that it overtakes and diminishes the other. In this writer’s opinion, the most severe distortions are committed by peccability advocates who discount Christ’s divine person as the subject of Christ’s incarnate activity. - Could Jesus Have Sinned?

Nevertheless there are some Christians, like Dr. John Bechtle that make the following case for the idea that Jesus could not have sinned:

Christian churches generally agree that:

1. Jesus never sinned, but he was tempted.

For we do not have a high priest who cannot sympathize with our weaknesses, but one who has been tempted in all things as we are, yet without sin (Heb. 4:15 NASB).

2. Any temptations he faced were directed at His human nature, rather than His divine nature.

Let no one say when he is tempted, ‘I am being tempted by God’; for God cannot be tempted by evil, and He Himself does not tempt any one (James 1:13 NASB).

Some theologians, such as Charles Hodge, have argued that Christ could have sinned. Their main argument is that temptation is not real unless there is a possibility of yielding to it.

Others (with whom I agree) make the following case for the idea that Jesus could not have sinned.

It is possible to attempt the impossible, and temptation is merely Satan’s attempt to lead us astray. Temptation and susceptibility do not have to go together; only successful temptation always goes hand in hand with susceptibility.

• All the temptations Jesus faced in Matthew 4 were legitimate offers. The struggle in Gethsemane was a real, difficult experience. One might even say that Jesus experienced worse temptation than we do, because we usually surrender before the devil brings out his worst weapons. Jesus stayed firm through the most powerful temptations in Satan’s arsenal.

• Although the human nature of Jesus may have had desires which temptation could target, His divine nature would ensure that He would never actually decide to sin. It is impractical to speculate on what Christ’s human will might have decided if it were operating independently of His divine nature; such a situation never arose.

Christ’s divine attributes would make it impossible for him to sin:

• Immutability - His basic nature never changes (Hebrews 1:12; 13:8). He was holy in eternity past, and He would remain holy now.

• Omnipotence - Falling to temptation shows moral weakness or lack of power and ability. Christ had infinite power, and was therefore not susceptible to sin.

• Omniscience - Satan tempts us by attempting to deceive us. Jesus had infinite knowledge, so he could not be deceived.

Could Jesus Christ have sinned?

There are clearly two sides to this question. It is important to remember that this is not a question of whether Jesus sinned. Both sides agree, as the Bible clearly says, that Jesus did not sin (2 Corinthians 5:21; 1 Peter 2:22). However for Dr. John Bechtle to state that “their main argument is that temptation is not real unless there is a possibility of yielding to it,” is at odds with many Christian interpretations on this subject matter. Jesus in his human nature was definitely tempted as the rest of humanity. How can Jesus (or anyone) be really tempted if he could not sin? He was truly Man and truly God, for the historical Jesus had both a divine nature and a human nature.

You said, “We know he had his own will which differed from God's. Satan knew this when he tried to tempt Jesus into exercising his own will for selfish purposes. [Then you quoted, "For I have come down from heaven not to do my will but to do the will of him who sent me" John 6:38 & "Take this cup from me. Yet not what I will, but what you will” Mark 14:36.]”

But surely those verses prove that Jesus’ will was exactly the same as his Father’s will? Yes, he had his own will, but he chose to conform it utterly to the will of the Father. And who but he who had come from the bosom of the Father could know utterly the pefect and complete will of the Father? (See John 1:18.) The first verse you quoted shows that, before he came down from heaven to become the man, Jesus, he had decided to do what the Father willed. That included agreeing to be sent to earth to become flesh. He was not forced to become man, against his pre-human will! The second verse shows that right at the point before the crucifixion, his will remained resolutely the will of the Father. A third verse (Matthew 26:53-54) shows that the reason why he did not ask the Father to send twelve-plus legions of angels to deliver him at Gethsemane was that he knew such a request would stop the scriptures being fulfilled. He trusted in deliverance according to the will of the Father as in Psalm 119:170 – “Let my supplication come before thee: deliver me according to thy word.” And this, I suggest, is a recurring theme at every point where Jesus was tempted.

Still in Gethsemane, Jesus said, “I say unto you that this that is written must yet be accomplished in me” (Luke 22:37). A couple of hours or so earlier he had said, “And truly the Son of man goes as it was determined” (Luke 22:22). And, on the point of death on the cross, we are told, “Jesus knowing that all things were now accomplished, that the scripture might be fulfilled said, ‘I thirst’.” (John 19:28) Likewise, years earlier, when tempted by Satan, Jesus’ total command of, and belief in, the scriptures was key to him never sinning. The answer to your main question, ‘What is the biblical basis that Jesus could not sin?’ is that Jesus is the Word of God, and knew every word written in scripture to be the holy word of God which he spoke in order to resist temptation – because he agreed 100% with that written word. How could he not, given that he was the very Word of God incarnate (John 1:1-14)?

Jesus could only sin if there was any part of the holy scriptures he personally disagreed with. The Psalmist said, “Thy word I have hid in my heart, that I might not sin against thee” (Ps. 119:11). Jesus being the Greater David, David’s Lord, knew every jot and tittle of that written word, employing appropriate quotations from the scriptures to defeat Satan’s temptations, and any other temptation along the way to death on a cross. The eternal Son could say even more meaningfully than the writer of Psalm 119:89, “For ever, O Lord, thy word is settled in heaven.” It was settled there before any creation began and the Son, "who made everything that was made” had a settled will in total accord with the will of the Father

Consider also how Jesus is the Last Adam (Rom. 5:14-18; 1 Cor. 15:21-22 & 47). Satan cunningly deceived the first woman into thinking she could elevate herself to be as God with a special knowledge that God had warned against, and the first Adam chose to go along with that rather than risk losing what was precious to him. The Last Adam was tempted by Satan with an offer to short-circuit the cross – to obtain worldly glory and elevation there and then. Satan knew Jesus was physically weak and hoped to appeal to physical desires (for instant food, for instant heavenly deliverance, for instant glory and power) because he knew Jesus was now made lower than the angels. He tempted Jesus to use his divine powers for personal gratification. But Jesus rebuffed all three temptations with correct use of scripture. Sure, Satan knew he was dealing with the incarnate Son of God, but he could not resist the chance to at least try to trip him up while in a weakened state, just as he had ensnared the first Adam by getting him to make a personal, selfish choice that showed he did not believe God's word to him.

Finally, those who do not believe Christ to be the eternal Son of God but to have been created either as the first of God’s creations or only to have come into existence when conceived as the virgin Mary’s child, will think it perfectly possible that this creature could have sinned. Those who take a higher view of Christ as the uncreated Word of God disagree, and they have a deep biblical basis for so saying. I have only scratched the surface of this matter, but it all boils down to, “What think ye of Christ?” (Matthew 16:15 & 22:42)

You went on to ask what the biblical basis for him not being able to sin could be. Given that the Bible does not even ask that question, but does show us why Jesus did not sin, I would suggest that grasping the biblical information provided will cause those who believe it to ask different questions.

I copied this answer from this website. The contents reflect what I have generally heard put forth to propose and defend the impeccability of Jesus. I have emboldened what I think is the heart of the proposition. The area in italics is where I believe a strong weakness in the proposition lies as it does not address being tempted to that which is impossible but undesirable. In other words, the question of impeccability "Can one be tempted to do that which one absolutely cannot do?" (such as turn into a mosquito and bite someone) is not addressed. The second emboldened part is epic failure (James 1:13).

There are two sides to this interesting question. It is important to remember that this is not a question of whether Jesus sinned. Both sides agree, as the Bible clearly says, that Jesus did not sin (2 Corinthians 5:21; 1 Peter 2:22). The question is whether Jesus could have sinned. Those who hold to “impeccability” believe that Jesus could not have sinned. Those who hold to “peccability” believe that Jesus could have sinned, but did not. Which view is correct? The clear teaching of Scripture is that Jesus was impeccable—Jesus could not have sinned. If He could have sinned, He would still be able to sin today because He retains the same essence He did while living on earth. He is the God-Man and will forever remain so, having full deity and full humanity so united in one person as to be indivisible. To believe that Jesus could sin is to believe that God could sin. “For God was pleased to have all his fullness dwell in him” (Colossians 1:19). Colossians 2:9 adds, “For in Christ all the fullness of the Deity lives in bodily form.”

Although Jesus is fully human, He was not born with the sinful nature that we are born with. He certainly was tempted in the same way we are, in that temptations were put before Him by Satan, yet He remained sinless because God is incapable of sinning. It is against His very nature (Matthew 4:1; Hebrews 2:18, 4:15; James 1:13). Sin is by definition a trespass of the Law. God created the Law, and the Law is by nature what God would or would not do; therefore, sin is anything that God would not do by His very nature.

To be tempted is not, in and of itself, sinful. A person could tempt you with something you have no desire to do, such as committing murder or participating in sexual perversions. You probably have no desire whatsoever to take part in these actions, but you were still tempted because someone placed the possibility before you. There are at least two definitions for the word “tempted”:

1. To have a sinful proposition suggested to you by someone or something outside yourself or by your own sin nature.

2. To consider actually participating in a sinful act and the possible pleasures and consequences of such an act to the degree that the act is already taking place in your mind.

The first definition does not describe a sinful act/thought; the second does. When you dwell upon a sinful act and consider how you might be able to bring it to pass, you have crossed the line of sin. Jesus was tempted in the fashion of definition one except that He was never tempted by a sin nature because it did not exist within Him. Satan proposed certain sinful acts to Jesus, but He had no inner desire to participate in the sin. Therefore, He was tempted like we are but remained sinless.

Those who hold to peccability believe that, if Jesus could not have sinned, He could not have truly experienced temptation, and therefore could not truly empathize with our struggles and temptations against sin. We have to remember that one does not have to experience something in order to understand it. God knows everything about everything. While God has never had the desire to sin, and has most definitely never sinned, God knows and understands what sin is. God knows and understands what it is like to be tempted. Jesus can empathize with our temptations because He knows, not because He has “experienced” all the same things we have.

Jesus knows what it is like to be tempted, but He does not know what it is like to sin. This does not prevent Him from assisting us. We are tempted with sins that are common to man (1 Corinthians 10:13). These sins generally can be boiled down to three different types: “the lust of the flesh, the lust of the eyes, and the pride of life” (1 John 2:16 NKJV). Examine the temptation and sin of Eve, as well as the temptation of Jesus, and you will find that the temptations for each came from these three categories. Jesus was tempted in every way and in every area that we are, but remained perfectly holy. Although our corrupt natures will have the inner desire to participate in some sins, we have the ability, through Christ, to overcome sin because we are no longer slaves to sin but rather slaves of God (Romans 6, especially verses 2 and 16-22).