Thank you for the question on Indulgences, “Are indulgences mentioned in the Bible?”
According to the Catholic teaching, the definition and reasons for Indulgences are as follows:
“Indulgence, a distinctive feature of the penitential system of both the Western medieval and the Roman Catholic Church that granted full or partial remission of the punishment of sin. The granting of indulgences was predicated on two beliefs. First, in the sacrament of penance it did not suffice to have the guilt (culpa) of sin forgiven through absolution alone; one also needed to undergo temporal punishment (poena, from p[o]enitentia, “penance”) because one had offended Almighty God. Second, indulgences rested on belief in purgatory, a place in the next life where one could continue to cancel the accumulated debt of one’s sins, another Western medieval conception not shared by Eastern Orthodoxy or other Eastern Christian churches not recognizing the primacy of the pope.”
https://www.britannica.com/topic/indulgence
One can perceive the danger of easy “forgiveness” by God to a “repentant” believer. It’s human nature to sin and if there is no “consequences” or seemingly no consequences, then what is the reason to stop sinning if I have to say to God, “I am sorry.” and continue on my merry way and do it again. There seems to be a lack of accountability against sin. Thus the Catholic Church concluded that a penance system is need to hold its members accountable through the Church.
Does the Bible support Indulgence? Though there may be some Scripture text that may be interpreted as in John 20 says this, “Again Jesus said, “Peace be with you! As the Father has sent me, I am sending you.” 22 And with that he breathed on them and said, “Receive the Holy Spirit. 23 If you forgive anyone’s sins, their sins are forgiven; if you do not forgive them, they are not forgiven” (NIV). It appears that the Lord is giving the Apostles the authority to forgive or not to forgive sin.
My understanding of that text is that when a believer is offended by another person, God calls the believer to forgive that person. The offense is against the believe and against God. If the offender refuses to repent of his/her sin, then God still holds that person accountable for that sin even though the believer forgives the offender. The believer is free of anger and leaves the judgment of God on how he will deal with the offender. If the offender is repented toward the offended party and to God, that person receives forgiveness of sins. God is the one who looks at the heart of the offender and the offended party.
In my understanding of the Scriptures to impose penance that affects one’s salvation is incorrect. Salvation is a gift from God and no condition can be placed on it.
One can place condition on being part of the local church for refusing to repent as loss of membership, not serving Communion to that person or even fellowshipping with that person, but not on his/her salvation. A church has the right to establish membership rules for its rules. Thus many Protestant churches have membership that asks its member to adhere and violations of those rules may bring church discipline to correct such conduct. The local church doesn’t determine the condition of one’s salvation.
The Scripture states that every believer will give an account of his life before the Lord whether good or evil. II Cor. 5 says this, “Therefore we are always confident and know that as long as we are at home in the body we are away from the Lord. 7 For we live by faith, not by sight. 8 We are confident, I say, and would prefer to be away from the body and at home with the Lord. 9 So we make it our goal to please him, whether we are at home in the body or away from it. 10 For we must all appear before the judgment seat of Christ, so that each of us may receive what is due us for the things done while in the body, whether good or bad” (NIV).
No one gets away with sin for God disciplines those whom he loves even as earthly parents discipline their children according to what they think is good for them, but God knows what is good for his children (Heb. 12:6).
SUMMARY: God desires more than a mere outward conformity to his Word, but an inward inclination toward his Word. Conditional salvation violates the biblical teaching that salvation is apart from any good works (Eph. 2:8–9).
For more perspectives:
https://www.quora.com/Are-indulgences-mentioned-in-the-Bible