Why is it not a sin when God asked Moses to lie to Pharaoh?

In the early stages in Exodus 3:18, it could have been genuinely God's intention that they go three days journey into the wilderness and then return, as the first act of a long process of escaping from Egypt. Only later did the plan change. So Pharaoh was not told a lie, just when the plan had changed he was not informed of the change of plan. To withhold information is not the same as telling a lie.

However, we are not under obligation to tell the whole truth to our enemies, or to those who are of lower authority to us. Though we should avoid lying, there are times when it is inevitably the right thing to do. When Corrie Ten Boon was hiding Jews in her house, and German soldiers asked her if there were any Jews in her house, she said "No". She lied in order to save lives. She lied because she believed it was more important to love the Jews and save lives rather than tell the truth. The importance of loving your neighbour and save their life takes a higher priority than telling the truth.

In time of conflict we are not obliged to tell the truth: if Hitler had phoned up Winston Churchill and asked him whether he was going to attack the Normandy Beaches or somewhere else, it would be absurd to think that Churchill must tell him the truth, or even try not to answer. Surely he can lie to his heart's content; and the bigger and more convincing the lie, the better.

Someone who would be quite happy to destroy us, contrary to the law of God, is not entitled to the truth from us.

Another example is Rahab hiding the spies and lying to the Canaanites (Joshua 2:3-7). Is this the moral equivalent of a lie contrary to God's law? I think it is not. And Hebrews 11:31 seems to confirm that what she did pleased God in that He says she did it by faith.

Also see Exodus 1:15-21. God blessed the midwives for what we would call "lying": but perhaps we need to use another word for it, such as "tricking"(?), to distinguish it from (immoral) lying? Not that using a different word makes it right... it was right already.

Another example is our Lord Jesus in John 7:8-10. His brothers are not entitled to know everything. Jesus is not under their authority. What He said when He said it was true: but He chose not to tell them the whole truth, that He was going up a little while later. He was not under any obligation to tell them everything.

For more on this see "Evangelical Ethics" by John Jefferson Davis, chapter 1, Dimensions of Decision Making, and the section headed "Cases of Conflicting Obligation". He also mentions Acts 5:27-29, where again, one of God's requirements, spoken of in Romans 13:1-2, is trumped by a higher obligation, to obey God. [I think Christians of all persuasions would like this book, it shows how close is agreement between all who want to worship God. It discusses issues from a Biblical perspective. Its chapters are Dimensions of Devision Making; Contraception; Reproductive Technologies; Divorce and Remarriage; Homosexuality; Abortion; Infanticide & Euthanasia; Capital Punishment; Civil Disobedience and Revolution; and War and Peace.]

Short answer: That was the truth. The plagues, etc. came about because Pharaoh wouldn’t give them three days.

As others correctly note, God knew in advance that Pharaoh would refuse the seemingly unimposing request that Moses presented to him; allow the people of Israel to journey three days into the wilderness to sacrifice to God. That Pharaoh refused is somewhat understandable. Like any tyrannical ruler he would assume that allowing an enslaved body of people to collectively embark on a three day journey away from their regular places of abode, equated to his giving a subservient people a small taste of freedom, and that in turn would likely unite them in spirit and possibly result in a major uprising. Pharaoh and his counselors perhaps believed that of all who departed on a three-day journey into the wilderness, not all would return, speculating that various families or individuals would take advantage of the three-day excursion and plot an escape from Egypt.

Some may perhaps believe Moses (or God) was being a little coy with Pharaoh, perhaps even somewhat deceptive? Perhaps a belief is that if Pharaoh had in fact allowed the people of Israel to travel three days into the wilderness to sacrifice to God, the people would thereafter not return back to their Egyptian homes.

Momentarily assume Pharaoh gave in to Moses' request. Momentarily assume that under Pharaoh’s approval Israel was allowed to travel three days into the wilderness to sacrifice to their god. What then can we safely assume would have happened? Knowing God’s commitment to deliver Israel from Egyptian enslavement motivates us to believe the people of Israel would simply have continued their journey out of Egypt, leaving Pharaoh to feel he had been duped. If such happened, then the scenario might be as follows; Pharaoh, some three or so days after the people of Israel had traveled away, received word from his messengers, informing him that Israel didn't just offer sacrifices to their God after three days of travel, but instead they were heading straight for Egypt’s border. Kindly allow me to offer a different perspective, a belief that the children of Israel would have done exactly as Moses said, or perhaps said more correctly, they would have done what Pharaoh, in his mind, believed he was hearing Moses say, that is, Moses was requesting that the people of Israel be allowed to travel three days into the wilderness to sacrificed to God, and then afterwards they would return back to their homes. If Israel had returned from the wilderness as Pharaoh presumably was allowed to believe, then Pharaoh could never point a finger at Moses (or God) and say, I trusted your words, but in return you pulled off a real sneaky on me, I was deceived.

A fair question is, after traveling three days into the wilderness, why would Israel choose to return back to their homes anyway, back to conditions of slavery, especially when they knew that God's plan was for the people of Israel to not just go on a three day trek into the wilderness to offer sacrifices, but was instead that they depart altogether from Egypt? Several points to consider; first, a three-day journey into the wilderness by a massive army of people, with all returning back to their Egyptian homes afterwards, would provide some excellent traveling experience for a people formerly inexperienced in such an endeavor. Equally important, the three days going and three days returning would serve to fine-tune Israel's preparations for what ultimately lay ahead, a truly long walk out of Egypt.

On the other hand, a three day journey into the wilderness, followed by a subsequent refusal to return back to their homes, would essentially result in a largely impoverished people embarking on a strenuous journey, versus later, after Israel had observed the Passover, they left Egypt with a substantial amount of wealth bestowed upon them by the Egyptian populous.

Another point; as scripture says, God all along was going to deliver Israel from their enslavement under Pharaoh's authority, doing so by whatever means and manner He chose. Why then should it be thought that a short journey into the wilderness, followed by an immediate return to their homes and their enslaving job-occupations, would interfere with or somehow disrupt God's fulfillment of Israel’s promised deliverance?

For argument’s sake let’s momentarily assume that what God said wasn't going to happen, did happen, meaning let’s assume that Pharaoh actually allowed the people of Israel to travel three days into the wilderness, after which the people then, to Pharaoh’s satisfaction, returned to their homes. The position here is that if Pharaoh had given the people of Israel permission to journey three days into the wilderness, then under God’s direction the people of Israel would in reasonable time have returned back to their homes. Suggesting otherwise may unwittingly be arguing that God conjured up a scheme, a ploy if you will, to deceptively convince Pharaoh to let the people of Israel go, all the while allowing Pharaoh to believe that Israel was merely going on a three-day journey into the wilderness. However, all along, the supposition by some is, Moses knew that the people of Israel would in reality continue traveling further away from Pharaoh’s authoritative reach. Even if Pharaoh had granted Israel leave, and even if Israel had returned back to their homes following their three-day journey into the wilderness, Moses would yet again be found standing before Pharaoh, and God's plan would continue on unabated.

From scripture we know that God told Moses that Pharaoh would deny the requested three-day wilderness journey. Why then even bother having Moses ask Pharaoh to give the people of Israel permission to journey three days into the countryside just to offer sacrifices to God? Why the futile request? What rises out of the biblical narrative is; before the weight of God’s deliver-Israel plan was fully activated, God first gave Pharaoh an opportunity to exhibit some mercy, to perform an act of kindness by his allowing an enslaved people to enjoy a short seven to perhaps ten day break from their harsh routines. Pharaoh was given an opportunity to let Israel enjoy a brief period of relaxation, to experience some enjoyable family time together as a people. Allowing an excessively overworked people to have a momentarily reprieve could have been a little thing for Pharaoh. And, the enslaved people would probably then begin viewing Pharaoh in a more favorable light. Also, allowing an enslaved and unarmed people to travel say some 40 to 50 or so miles away from the day-to-day hubbub and turmoil of their Egyptian existence, thereby allowing them to enjoy a short vacation so to speak, would have been an a manageable risk for Pharaoh. Officials and spies would have kept a close eye on subsequent events, and if anything were to go awry Pharaoh’s mighty army would have received their marching orders; except for God’s protection (something Pharaoh didn’t know they had) the slaughter may have been enormous.

So why request just a three-day journey into the wilderness anyway, especially given the fact that God knew what Pharaoh’s response was going to be beforehand? What God did, that is what He did by having Moses ask Pharaoh to allow Israel to enjoy a brief reprieve, is somewhat comparable to a show-and-tell classroom type demonstration. Moses was instructed to submit a seemingly unimposing request to Pharaoh – let Israel travel three days into the wilderness to sacrifice to God – which Moses knew Pharaoh would not allow. However, the request by Moses and refusal on Pharaoh’s part would thereupon provide an unquestionably clear message for all of Israel, the message being that Pharaoh would never entertain any ideas of ever allowing the enslaved people of Israel to now-and-then enjoy some forms of relief from their current endless days of hard labor. The request and its rejection by Pharaoh was a message Israel needed to hear, that hard labor was going to be their plight throughout life if, that is, they remained in Egypt.

As a side note, in contrast to Pharaoh’s uncompromising lack of compassion and mercy for an enslaved people, his unshakable resolve to never allow a trodden-down nation of people, Israel, to enjoy even a small measure of relief, enjoying a temporary break from the struggles of their enslavement, God instead, upon His pouring out plague after plague on Egypt would always, whenever Pharaoh withdrew from his belligerent state and asked for relief from a plague, provided what relief could be provided.

From the following scripture, among others, we know that God cannot lie:

Titus 1:2 (RSVCE) 2 in hope of eternal life which God, who never lies, promised ages ago

Therefore we know for certain that God was not sending Moses and the elders of Israel to lie with the said words. (Also, God is not and cannot be the author of sin).

The question would be more of a conundrum if the Exodus passage added:

let us go three days’ journey into the wilderness, that we may sacrifice to the Lord our God, thereafter, we shall return.

What therefore is the explanation? What may be understood by these words? What did God actually mean by these words?

The Navarre Bible Pentateuch Note on Exod 3:16-22 has in part:

The three days' journey (v. 18) would not take them to Sinai but was enough to get them away from Egypt. Later, three days will become a number symbolizing divine action. See note on 6:10-13.

The note on Exod 6:10-13 has in part:

According to this "Priestly tradition" account Moses has to win the total (my emphasis) freedom of the people, not just get permission for a three-day pilgrimage (cf. 3:18; 5:1).

Therefore understanding that in Jewish tradition the number three (3) signifies completeness and stability¹, this appears to have been the meaning of the words, i.e. 3 days meant getting the Israelites definitively away from Egypt so that they may always worship God in total freedom.

^{1. cf. Judaism & Numbers, Jewish tradition values some numbers more than others. By Rabbi Geoffrey Dennis.}

Endnote

Lying, as defined by St. Thomas Aquinas, is a statement at variance with the mind.cf. [Lying | New Advent].

For God to have been lying, one would have to show that what he was saying was at variance with what he was thinking. And who knows the mind of God? The next best things is to try to reconcile and explain as I have attempted to do above.