Isaiah 43:25 I, even I, am he who blots out your transgressions, for my own sake,and remembers your sins no more. If God forgives for His own sake, should we? Perhaps yes, but we should forgive primarily for His sake because He forgave us (Colossians 3:13 Forgive as the Lord forgave you). The context of this vibrant poetry is God’s own character. God overflows with love and compassion for His people, who have spent years in exile. He redeems them (Isaiah 43:1; 14). In this, His holiness is exalted (Isaiah 43:3, 14, 15).
The basis for forgiving others is rooted in our new life in Christ. We are forgiven by means of His atoning death. Colossians 2:13-14 When you were dead in your sins and in the uncircumcision of your flesh, God made you alive with Christ. He forgave us all our sins, 14 having canceled the charge of our legal indebtedness, which stood against us and condemned us; he has taken it away, nailing it to the cross. We are declared righteous: Romans 3:24 and all are justified freely by his grace through the redemption that came by Christ Jesus. We are empowered by His Spirit to live this new life. Romans 8:11 And if the Spirit of him who raised Jesus from the dead is living in you, he who raised Christ from the dead will also give life to your mortal bodies because of his Spirit who lives in you.
We forgive because Christ forgave us (Ephesians 4:32 Be kind and compassionate to one another, forgiving each other, just as in Christ God forgave you); it is a natural expression of our redemption and a law of the thankful heart. And in forgiving, we ourselves are blessed and freed to love others through Christ.