“And immediately he arose, took up the bed, and went forth before them all; insomuch that they were all amazed, and glorified God, saying, We never saw it on this fashion.”
He got up, took his mat and walked out in full view of them all. This amazed everyone and they praised God, saying, we have never seen anything like this! — the triple action (got up, took, walked) mirrors the triple command of verse 11. The full view of them all ensures the witness is comprehensive and undeniable. The response is universal amazement followed by praise of God — the crowd correctly identifies the healing's source even without fully grasping its Christological implications. We have never seen anything like this is the only response adequate to what has just happened: not just healing but the demonstration of authority to forgive sins on earth through visible, verifiable, miraculous action.
Church Fathers on Mark 2:12
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.