The Bible addresses forgiveness directly in several passages:
Matthew 6:14-15 (KJV)
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.
Ephesians 4:32 (KJV)
32 And be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ’s sake hath forgiven you.
Colossians 3:13 (KJV)
13 Forbearing one another, and forgiving one another, if any man have a quarrel against any: even as Christ forgave you, so also do ye.
1 John 1:9 (KJV)
9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.