Seventy times seven is not a number in this instance; if it is, it is infinity. Forgiveness, not a number, is the message from Jesus.
This Parable of the Unmerciful Servant is the ending of a series of teachings following the Transfiguration where Jesus talked with Moses and Elijah. Being faithful to God is the overall theme of the lessons, much as the Israelites, but mostly Moses, obeyed God in crossing the sea.
Jesus describes the greatest of his followers to be child-like in their faith. He points out that seeking the lost is part of the duties of following Jesus. He moves next to the importance of seeking reconciliation with any other followers who may have done a wrong against us. And now he adds that forgiveness is also a critical part of following Jesus.
Why forgive? Because God forgives us. He forgives us 70,000 times 70,000 and more after that. He forgives us because He loves us and has called us to love Him and to love others. Tremble, Earth! You’re in the Lord’s presence! in the presence of Jacob’s God. MSG If His love and forgiveness is not enough, we should at least tremble in his presence. He commanded the sea to stand and a rock to give water.
There is no end to either His power or His love.
Be righteous and do good.