“When Jesus saw their faith, he said unto the sick of the palsy, Son, thy sins be forgiven thee.”
When Jesus saw their faith, he said to the paralyzed man, son, your sins are forgiven — the most striking detail of this verse is that Jesus sees the faith of the four bearers and responds by forgiving the sins of the paralyzed man. The faith that produces the forgiveness is not the paralyzed man's own (he has not spoken or acted) but the faith of his friends, enacted through the roof-opening. This is the New Testament's clearest example of faith-on-behalf-of-another producing healing and forgiveness — intercession enacted through action rather than words. The address son (teknon, child) is warm and intimate. The forgiveness precedes the healing, communicating that the deeper need is addressed first.
Church Fathers on Mark 2:5
Because the compassion of God deserts not even carnal persons, He accords to them the grace of His presence, by which even they may be made spiritual. After the desert, the Lord returns into the city.
But Matthew writes this miracle as if it were done in the city of the Lord, whilst Mark places it in Capernaum, which would be more difficult of solution, if Matthew had also named Nazareth. But seeing that Galilee itself might be called the city of the Lord, who can doubt but that the Lord did these things in His own city, since He did them in Capernaum, a city of Galilee; particularly as Capernaum was of such importance in Galilee as to be called its metropolis?
He saw the faith of the sick man himself, since he would not have allowed himself to be carried, unless he’d had faith to be healed.