Sirach 28:1
Ben Sira, Ecclesiasticus1 The vengeful will face the Lord's vengeance, for he keeps a strict account of their sins. 2 Forgive your neighbor the wrong he has done, and then your sins will be pardoned when you pray. 3 Does anyone harbor anger against another, and expect healing from the Lord? 4 If one has no mercy toward another like himself, can he then seek pardon for his own sins? 5 If a mere mortal harbors wrath, who will make an atoning sacrifice for his sins? 6 Remember the end of your life, and set enmity aside; remember corruption and death, and be true to the commandments.
Matthew 18:23
23 “For this reason, the kingdom of heaven is like a king who wanted to settle accounts with his slaves. 24 As he began settling his accounts, a man who owed 10,000 talents was brought to him. 25 Because he was not able to repay it, the lord ordered him to be sold, along with his wife, children, and whatever he possessed, and repayment to be made. 26 Then the slave threw himself to the ground before him, saying, ‘Be patient with me, and I will repay you everything.’ 27 The lord had compassion on that slave and released him, and forgave him the debt. 28 After he went out, that same slave found one of his fellow slaves who owed him 100 silver coins. So he grabbed him by the throat and started to choke him, saying, ‘Pay back what you owe me!’ 29 Then his fellow slave threw himself down and begged him, ‘Be patient with me, and I will repay you.’ 30 But he refused. Instead, he went out and threw him in prison until he repaid the debt. 31 When his fellow slaves saw what had happened, they were very upset and went and told their lord everything that had taken place. 32 Then his lord called the first slave and said to him, ‘Evil slave! I forgave you all that debt because you begged me! 33 Should you not have shown mercy to your fellow slave, just as I showed it to you?’ 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
"... In Matthew’s Gospel we see the idea of reciprocity, the idea of conditionality, the link between mercy and forgiveness and the punishment that comes for reluctance to practise mercy/forgiveness. For the first Evangelist, refusing to show mercy to or to forgive others leads to God’s refusal to do the same to the unmerciful or unforgiving person. More than that, it calls for punishment upon them. This is powerfully stated in the parable of the unmerciful debtor in Matthew 18:23-35 and implicitly in Matthew 6:15. Demands to be merciful (Matt 5:7), not to retaliate (Matt 5:21-23), and not to judge (Matt 7:1-2) are also implied in this reading.45 This brings about the notion of accountability in forgiving ... The idea of accountability as related to mercy and forgiveness is very rare in biblical Judaism. Sirach 28:1-7 is the only very close early Jewish parallel. Verses 1-4 are most relevant ..."
Mbabazi, Isaac Kahwa The Jewish Background to Interperonal Forgiveness in Matthew (pp. 15-34) Africa Journal of Evangelical Theology 30.1, 2011