When I was a child, I remember doing a thing that was wrong. Now as an adult, I’m curious about confession of that sin. For example, is confession to my spouse sufficient? Or does God require us to confess to multiple people including the people sinned against?
Regarding personal confession to others, the Bible directs us to confess our sin to other believers as a means of strengthening each other’s walk with Christ:
James 5:16 Therefore, confess your sins to one another, and pray for one another so that you may be healed. The effective prayer of a righteous man can accomplish much.
James is not requiring we confess our sin to those we offended specifically, though that may be possible as well. The intention is to be transparent and honest with other believers about our weaknesses so they may pray for us and encourage us to better things.
Similarly, Christ says it’s more important to God that we seek to restore our relationship with an offended brother (a fellow believer) before we seek to repair our relationship with an offended God.
Matt. 5:23 “Therefore if you are presenting your offering at the altar, and there remember that your brother has something against you,
Matt. 5:24 leave your offering there before the altar and go; first be reconciled to your brother, and then come and present your offering.
Jesus’ point is that those who willingly and unrepentantly offend fellow believers are playing the hypocrite when they turn to God seeking forgiveness.
On the other hand, our choice to confess in any particular situation is a matter of personal conviction. If you feel convicted by the Spirit to confess a specific sin to another person, then you should follow that conviction. At the very least, you should confess your sin in prayer to the Father, for by this confession you may grow in your sanctification and personal holiness, walking according to the same grace you have received from Christ by faith.
Ultimately, all our sin was forgiven at the moment of our confession of faith, as you stated:
1John 1:8 If we say that we have no sin, we are deceiving ourselves and the truth is not in us.
1John 1:9 If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness.
So beyond these instructions, the Bible places no burden on believers to confess systematically to every person we offend (is this even possible?). Confess your sin in prayer, follow your conscience in confessing to others, and do not feel burdened otherwise.