II Corinthians 2:10-11
"To whom ye forgive any thing, I forgive also; for if I forgave anything, to whom I forgave it, for your sakes forgave I it in the person of Christ; lest Satan should get an advantage of us; for we are not ignorant of his devices". (King James Bible)
(Comment: We are to forgive quickly so Satan will not be able to plant a "root" in us of evil. For now we are aware of his tactics and characteristics to not let them take hold of us.)