This is one of the few Catholic Doctrines that you will actually find explicitly mentioned in Scripture. Even so, Protestants deny it.
Confess your sins
1 John 1:9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
They deny that this is a reference to the Sacrament of Confession because they don’t see the “confessional” described there. But that is a straightforward reference to confession of sins. In company with the rest of the verses I'll provide, there is no doubt in my mind that it is a reference to the Sacrament.
Ministry of reconciliation
Well, the “confessional” imay neither be mentioned nor described in Scripture, but there is a reference to the ministry of reconciliation, which in my opinion is a reference to the Sacrament of Reconciliation (CCC#1461). Which, if you’re Catholic, you know is the same thing as Confession.
2 Corinthians 5:18 And all things are of God, who hath reconciled us to himself by Jesus Christ, and hath given to us the ministry of reconciliation; 19 To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation. 20 Now then we are ambassadors for Christ, as though God did beseech you by us: we pray you in Christ's stead, be ye reconciled to God.
Read verse 20 and think about what happens in the confessional. Doesn’t the priest pray for you in person of Christ? Are you not then reconciled to God? And here's something else which happens in the confessional.
Submit and obey
Again, think about what happens when you go to Confession. And read this:
Hebrews 13:17 Obey them that have the rule over you, and submit yourselves: for they watch for your souls, as they that must give account, that they may do it with joy, and not with grief: for that is unprofitable for you.
Let’s break this down.
1. obey and submit. That is effectively what we do when we go to a priest with the intent of confessing our sins. We have to come in with an attitude of humility and obedience, ready to do whatever we are told is necessary for us to be cleansed of our sins.
2. for they watch for your souls. Priests are our Pastors because God has appointed them to watch over our souls.
3. as they that must give account. Remember that the Priest has the God given authority to forgive or not to forgive.
CCC#1460 says, The penance the confessor imposes must take into account the penitent's personal situation and must seek his spiritual good.
What’s the rule about Confession?
For this one, you need to have a little background. Let’s start with a question. What’s the rule about Confession? How often do you need to confess your sins? Here’s the Canon Law:
After having reached the age of discretion, each member of the faithful is obliged to confess faithfully his or her grave sins at least once a year. (CIC 989)
Do you know why?
Have you ever heard of the Confiteore? The word means, “I confess” and it starts like this, “I confess to almighty God and to you my brothers and sisters….” Now you recognize it, right? You recite it at almost every Mass. This confession, remits your venial sins. Therefore, if you attend the Mass weekly and you have no mortal sins on your soul, you have fulfilled your requirement for Confession.
Now, let’s look at Scripture:
James 5:16 Confess your faults one to another, and pray one for another, that ye may be healed.
The Catholic Church does not teach us to confess to each other any where else. It is something which we do only in the Mass. Therefore, I believe this is a direct reference to the Confiteore, in the Mass.
Last, but not least
God gave our Priests the authority to forgive our sins. In fact, they can forgive or deny forgiveness. Without this authority, the Church could not forgive our sins. Therefore, Jesus explicitly gave the Church this authority.
Note that the statement is completely unambiguous. Jesus gives the Church the authority to forgive and not to forgive. That is how we know that this is a reference to the Sacrament of Confession, since, in another verse, Jesus condemns an unforgiving attitude (Matt 18:35). Here is what Scripture says:
John 20:23 Whose soever sins ye remit, they are remitted unto them; and whose soever sins ye retain, they are retained.
Thanks for your attention. Let me know what you think, below.