I must take great care not to cause him to sin. I must rebuke him when he sins and then forgive him. No matter how often he sins against me, if he confesses his sin I must forgive him. I no longer live, but Christ lives in me, and the life which I now live in the flesh, I live by faith in the Son of God who loved me and gave himself for me. No wonder that out text speaks of our need for genuine faith.
Christian faith is like a mustard seed.
If it is genuine, although it is small, it can do mighty things, not because of us but because of Christ. We sin much every day. Even Christians sin despite their best efforts. Forgiveness of sins is a miracle. It is like telling a tree to be uprooted and to be planted in the sea.