Testament of Gad 6:7
Testament of the Twelve Patriarchs[Let not another man hear thy secrets when engaged in legal strife, lest he come to hate thee and become thy enemy, and commit a great sin against thee; for ofttimes he addresseth thee guilefully or busieth himself about thee with wicked intent.] And though he deny it and yet have a sense of shame when reproved, give over reproving him. For he who denieth may repent so as not again to wrong thee; yea, he may also honour thee, and [fear and] be at peace with thee And if he be shameless and persist in his wrong-doing, even so forgive him from the heart, and leave to God the avenging.
Matthew 18:35
34 And in anger his lord turned him over to the prison guards to torture him until he repaid all he owed. 35 So also my heavenly Father will do to you, if each of you does not forgive your brother from your heart.”
Notes and References
"... The language of the fatherhood of God abounds in the Sermon and in the Community Discourse from which our two forgiveness texts are taken. As Robert H. Gundry has said, the manner in which the heavenly Father will deal with the unforgiving disciple leaves no room for misunderstanding the parable, and therefore no excuse for failure to forgive. The expression (“from your heart”) is important for the discussion. It also occurs in Testament of Gad 6:7 (“I forgive you from the heart”). In Matthew 18:35, it expresses sincerity and excludes all casuistry and legalism, as France has also suggested. The phrase (“from the heart”) shows that hypocrisy has no part in the kind of forgiveness that God demands. But the warning character of the parable shows that forgiving out of obedience need not kill sincerity, for a true disciple wants to obey his master. Commenting on the statement (“from the heart”), Luz says that forgiveness of sins involves both outward reconciliation with one’s brothers and sisters and complete affirmation of them. Sincerity is thus at the core ..."
Mbabazi, Isaac Kahwa The Jewish Background to Interperonal Forgiveness in Matthew (pp. 15-34) Africa Journal of Evangelical Theology 30.1, 2011