Is confessing to a priest the only way to be forgiven?

The only way to be forgiven is to repent of your sins and call upon Jesus Christ (Romans 10:9-13), believing that He died on the cross to pay the penalty for sins (Romans 6:23) and rose again after three days and now intercedes in heaven on behalf of those who belong to Him (1 John 2:1). We can only be justified by the work of Jesus Christ, and we can do nothing to save ourselves (Ephesians 2:8-9).

Confessing your sins to a priest in order to obtain favor with God is detestable to God, because that action says that what Jesus did on the cross was not sufficient for justification. Jesus is the one mediator between us and God (1 Timothy 2:5), and He alone is our Priest (Hebrews 3:1). Confession to fellow believers is prescribed (James 5:16), but it is not for the purpose of obtaining forgiveness from God.

There are several Bible verses that back confession.

Jesus Christ granted the Apostles His Authority to forgive sins:

John 20:21 - Since Christ was sent to forgive sins, and he sent the Apostles out to forgive Sins.

John 20:22 - When the Lord "Breathes" on someone, a significant transformation takes place. See the reference in Genesis.

John 20:23 - Jesus says, "If you forgive the sins of any, they are forgiven. If you retain the sins of any, they are retained." In order for the apostles to exercise this gift of forgiving sins, the penitents must orally confess their sins to them because the apostles are not mind readers. The text makes this very clear.

Matt. 9:8 - Demonstrates that the Apostles can forgive. Where in Scripture is the gift of authority to forgive sins taken away from the apostles or their successors?

Matt. 9:6

Mark 2:10

Luke 5:24

Matt. 18:18

John 20:22-23

Matt. 18:18

2 Cor. 2:10

2 Cor. 5:18

James 5:15-16

1 Tim. 2:5

Lev. 5:4-6; 19:21-22

The Necessity and Practice of Orally Confessing Sins

James 5:16

Acts 19:18

Matt. 3:6

Mark 1:5

1 Tim. 6:12

1 John 1:9

Num. 5:7

2 Sam. 12:14

Neh. 9:2-3

Sir. 4:26

Baruch 1:14

1 John 5:16-17

Luke 12:47-48

Matt. 5:19

There is also tradition in the Early Church Fathers.

See here for more Commentary: http://www.scripturecatholic.com/confession.html

Since there is Scriptural evidence going all the way back to the Old Testament, confession is necessary.

Ah confession. One of the seven sacraments in Roman Catholicism. Is it required? No. Can it help? Yes. If confessing to your pastor or priest helps you form a stronger relationship with Christ then go for it. Just make sure you remember who is doing the forgiving, not the pastor or priest but the one who died on the cross for the weakest of us. Thats just how I see it but United Methodists have always been pretty accepting

We have a biblical warrant to be thinking in the mindset of confession for the forgiveness of sins.

If we say we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. If we say we have not sinned, we make him a liar, and his word is not in us. (1 John 1:5-10 ESV)

Yet, a larger survey of forgiveness in the Bible yields us with plenty of examples and explanations of forgiveness which say nothing of confession.

But now the righteousness of God has been manifested apart from the law, although the Law and the Prophets bear witness to it—the righteousness of God through faith in Jesus Christ for all who believe. For there is no distinction: for all have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus, whom God put forward as a propitiation by his blood, to be received by faith. This was to show God's righteousness, because in his divine forbearance he had passed over former sins. (Romans 3:21-25 ESV)

The biblical model of forgiveness is justification, that is, God's declaration of righteousness, through propitiation that is, the appeas*m*nt of wrath, on the basis of the blood of Christ, which is received by faith, as a gift.

The idea is that when a sinner places their faith in Christ, God's wrath against that sinner is appeased as a free gift to them and accounted on the basis of Jesus' sacrifice.

Confession generally serves as an expression of faith, although there is no biblical prescription that priests be the sole mediators of this forgiveness. In fact, the idea that a priest would have exclusive authority or office in the mediation of confessions is directly refuted:

For there is one God, and there is one mediator between God and men, the man Christ Jesus, who gave himself as a ransom for all, which is the testimony given at the proper time. (1 Timothy 2:5-6 ESV)

The actual biblical prescriptions of confession are generally either directed to God (e.g. Psalm 51), or to one another:

Therefore, confess your sins to one another and pray for one another, that you may be healed. The prayer of a righteous person has great power as it is working. (James 5:16 ESV)

Nonetheless, there are traditions, most notably Roman Catholicism, which teach systems of sacraments, whereby the Church serves as a type of dispenser of various forms of God's grace. These graces are communicated through sacraments like Baptism, Confirmation, Eucharist, Penance, Anointing of the Sick, Holy Orders, and Matrimony. Confession would fall into the wider scope of Penance, and thus the tradition of confession to a priest for forgiveness.

Although Roman Catholic teaching would hold that this system is biblical, personally, I reject this notion of the sacraments. I think that the most biblical case can be made for the forgiveness of sins by faith, and that this faith would express itself as confession to God and to other believers.

Since the Catholic perspective has not yet been stated, and since the OP professed to be a member of a Church which is allied with Rome, it might be a good idea to state the RCC position here:

• Mortal sins are sins which cut off your relationship with God.
• Venial sins are all of the other sins.

A person who dies with venial sins on his soul will go to purgatory. A person who dies with a mortal sin on his soul will be condemned. Venial sins can be forgiven by a large number of things, most commonly, however, is that they are all forgiven (outright) by the very act of attending the penitential rite at Mass. (You should still confess these, but they will not merit purgatory). The prayer "May the Lord bless us, forgive us our sins..." is actually an absolution (I think the absolution is in the Eastern Trisagion Hymn, but I don't know).

Mortal sins are a little more tricky. They are normally (and most obviously) removed in the sacrament of reconciliation. However, it is possible to have them forgiven through perfect contrition, but part of that contrition includes the resolve to go to confession if available. It should also be noted that mortal sin can also be viewed under similar light as "baptism of desire". I am venturing into slightly ambiguous territory here (I've never actually seen this stated explicitly), but it seems to be consistent to believe that God will not damn a man who is on the way to confess his sins.

All of that said, we should also remember that simply because God has promised to work through the sacraments that does not mean that he will never work apart from the sacraments (Again, see doctrines surrounding invincible ignorance). We should also remember that the forgiveness comes from God and, even if we are using the sacrament of reconciliation, He is the one who is forgiving.

tldr; — forgiveness, even if it is through the sacraments, is still from God and only from God. He is the only way to be forgive.