Sirach 28:2
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?
Matthew 6:12
9 So pray this way: “Our Father in heaven, may your name be honored, 10 may your kingdom come, may your will be done on earth as it is in heaven. 11 Give us today our daily bread, 12 and forgive us our debts, as we ourselves have forgiven our debtors. 13 And do not lead us into temptation, but deliver us from the evil one. 14 “For if you forgive others their sins, your heavenly Father will also forgive you. 15 But if you do not forgive others, your Father will not forgive you your sins.
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