SIN, REPENTANCE AND REMISSION
First: All mankind are by nature "sinners". Ps 51:5 Behold, I was shapen in iniquity; and
in sin did my mother conceive me. [David speaking] Paul spoke to the subject in Romans
5:12; Because of the "sin" Of Adam in Eden, sin was pronounced upon all, for all have sinned.
Second all "sins" are not the same. There are sins against God, against the Holy Ghost, against our brother or fellowman. Fornication is a sin against the person's own body.
See 1st. Cor. 6: 18.
Third; All unrighteousness is sin, there is a sin "unto death" and also a "sin not unto death". There are two Greek words in the NT translated; sin or sins. The first is S# 266 "hamartia" [this word is a noun and is found 112 times in the NT. The governing principle of sin; using the body as an instrument to commit the act. The sin nature of mankind, The Adamic sin. The body of sin spoken of as "the old man". This also is referred to as the "Law of sin and death." Rom. 8: 2-4, see also ch. 6: 18-22, 7: 23-25, Gal. 2: 19-20, 5: 1.
This "sin" requires the regeneration or the "Born again" experience to eradicate. The other word is S# 264 "hamarthano" a verb, and is found 43 times in the NT. Denoting "a missing of the mark" or an act of sin committed by a person caused by "passion or by being overcome by lust or temptation. This "sin" requires repentance and sometimes "restitution" before forgiveness is received.
Sins that may require "restitution" are sins committed against another that has caused personal hurt or loss; i.e. as theft or causing damages to another's reputation. For example read Paul's letter to Philemon, concerning Onesimus; who had been a slave or servant of Philemon and had stolen from or had caused "hurt" to his master and now is "on the run" to avoid severe punishment and seeks Paul out in prison. Paul tells him to return home to make things right. He also sends this letter with him to Philemon that he would "act as security for Onesimus, who had "just been saved."
For Paul's instructions to "Christians" that need to repent; See 2nd. Cor. ch. 7: 1-16, These Christians had fallen into a state of "being unclean"; in other words; "they had sinned". See 1st. Cor. chapter # 5; The Corinthians had allowed "fornication" to become common in the Church. In that letter he told them to "withdraw fellowship" from the offenders.
In the second letter he gives instructions about restoring these "backslid" Christians to fellowship. It would through "godly sorrow" that would lead to repentance.
Next see the instructions in 2nd. ch. 2: 18-26 Timothy that Paul gave to Timothy the Bishop of the Church at Ephesus concerning some that had allowed their vessels to become "dishonorable because of sin". They were told to "purge" [cleanse by sanctification][themselves by repentance.
The Apostle John writes in 1st. John 2:1-2 says that Jesus is our "advocate" [the intercessor, the one who pleads our case] and the "propitiation" [the "mercy seat, the power of forgiveness] for "our sins".
Remember in the OT that the "sinner" was required to bring a lamb to the High Priest at the Temple to be slain and its blood be "sprinkled" on the "mercy seat" for their forgiveness of sin. Jesus is our "lamb" and has already been slain. But the individual that sins today must " come boldly to the throne of grace to find help." Heb. 4: 12-16.
Peter advises the Christians in 2nd. Peter 3: 9-12 concerning the coming of Jesus, that he is "longsuffering toward us" and not willing for us to perish because of "sin" but that all would "come to repentance". See also Romans 2: 4- 6.
The Apostle John in his letters to the churches on Asia wrote to the Church at Ephesus in ch. 2: 1-7, at Smyrna ch. 2: 8-11, at Thyatira ch. 2: 18-22, at Sardis ch. 3: 1-6 and at Laodiceia to repent for various reasons. Since these were the "last day" churches and they needed to repent; It is clear that Christians that are commanded "not to sin" 1st. Cor. 15: 34, Eph. 4: 26, 1st. John 2: 1, 5: 16-17 and yet we know that Christians do "commit acts of sins" these must be repented of, because sin will never enter Heaven.
Study very closely Romans chapters 5: -8 for a good understanding of the "Sin question".