Matthew 6:14-15

If you forgive those who sin against you, your heavenly Father will forgive you.  But if you refuse to forgive others, your Father will not forgive your sins.

Ephesians 4:32

Get rid of all bitterness, rage, anger, harsh words, and slander, as well as all types of evil behavior. Instead, be kind to each other, tenderhearted, forgiving one another, just as God through Christ has forgiven you.