“And, behold, they brought to him a man sick of the palsy, lying on a bed: and Jesus seeing their faith said to the sick of the palsy; Son, be of good cheer; your sins are forgiven.” Matthew 9:2 KJV
Faith can be seen. Just as Jesus explained to Nicodemus in John 3:8, faith is like the wind. Faith itself is invisible, but saving faith is always accompanied by actions that can be seen (Jas. 2:17-26). It was not the faith of only the paralytic that Jesus saw, but also that of his four friends (Mk. 2:3). This demonstrates the effect our intercession in faith can have upon others. Jesus saw their faith.
However, although our faith released on behalf of others is powerful, it is not a substitute for their faith; it is simply a help. The person who is to receive the miracle must also have some degree of faith. Even Jesus could not produce healing in those who would not believe (Mk. 6:5-6).
Why did Jesus minister forgiveness of sins to this man instead of meeting the obvious need he had of healing? Because God is more concerned with the spiritual health of a man than his physical health. Or, Jesus may have perceived that the real heart-cry of this man was to be reconciled to God. Through Jesus' act of forgiving this man's sins he was free to receive all the blessings of God, which included healing.