What does the Bible teach us about forgiveness?
In Matthew 6:12-15, we have this passage from the Lord's Prayer:
12 And forgive us our debts, as we also have forgiven our debtors.
13 And bring us not into temptation, but deliver us from the evil [one.]
14 For if ye forgive men their trespasses, your heavenly Father will also forgive you.
15 But if ye forgive not men their trespasses, neither will your Father forgive your trespasses.
In Mark 11:25-26, there's this similar one:
25 And whensoever ye stand praying, forgive, if ye have aught against any one; that your Father also who is in heaven may forgive you your trespasses.
26 [But if ye do not forgive, neither will your Father who is in heaven forgive your trespasses.]
In 1 Kings 8:38-40, there's another:
38 what prayer and supplication soever be made by any man, [or] by all thy people Israel, who shall know every man the plague of his own heart, and spread forth his hands toward this house:
39 then hear thou in heaven thy dwelling-place, and forgive, and do, and render unto every man according to all his ways, whose heart thou knowest; (for thou, even thou only, knowest the hearts of all the children of men;)
40 that they may fear thee all the days that they live in the land which thou gavest unto our fathers.
In Psalms 86:4-6, here's another excerpt:
4 Rejoice the soul of thy servant; For unto thee, O Lord, do I lift up my soul.
5 For thou, Lord, art good, and ready to forgive, And abundant in lovingkindness unto all them that call upon thee.
6 Give ear, O Jehovah, unto my prayer; And hearken unto the voice of my supplications.
From Isaiah, there's this:
Ah, sinful nation, laden with iniquity. When ye spread forth your hands, I hide Mine eyes from you; yea, when ye make many prayers, I do not hear. Wash you, put away the evil of your doings from before Mine eyes cease to do evil; learn to do well, and then shall your sins be removed and forgiven (Isaiah 1:4, 15-18).
What are the themes that start to emerge? Clearly, forgiveness is important. It works two ways, in that we need forgiveness from the Lord for our sins, and... that we need to forgive others. We need to make a supplication - a heartfelt prayer, before we are able to receive it. It's not that the Lord withholds is from us, but that - until we really feel remorse and humility and need - we aren't ready.
Here's a passage from Divine Providence n. 280:
Repentance must precede forgiveness, and apart from repentance there is no forgiveness. That is why the Lord told his disciples to preach repentance for the forgiveness of sins (Luke 24:27) and why John preached the baptism of repentance for the forgiveness of sins (Luke 3:3).
From Arcana Coelestia 8393, here's another one:
Being Mercy itself, the Lord is constantly forgiving a person's sins; but sins cling to a person no matter how much he supposes them to have been forgiven. Nor are they removed from him except through a life in keeping with the commandments of faith. To the extent that his life is in keeping with them his sins are removed; and to the extent that his sins are removed they have been forgiven.