NOTES for Mat 9:4-5
Sin and illness have always been connected in the consciousness of religious people. So it was in the Judaism of Gospel times. It was taken for granted that illness, especially serious illness, was the consequence of a sin committed by a person. If a person had been sick from birth, people thought that he suffered because of sins committed by his parents: it was assumed that the consequences of sin could spread to the sinner's whole family line. In order to recover, one had to repent sincerely of the sin committed, and then God, having forgiven the sin, could deliver the repentant person from the illness as well. And when Jesus tells the person He heals that his sins are forgiven, there is nothing unusual in this.
Except for one thing: it turns out that, saying this, He forgives sin on God's behalf. And this raises the corresponding questions in those who hear Him: indeed, only God Himself can forgive sins, so who is this strange wonderworker who puts Himself in God's place? If Jesus had simply healed the man, there would have been fewer questions: it would mean God's power acts through Him, and such a thing is possible. Something similar had happened before; miraculous healings had been known from ancient times, in particular through the prayers of righteous people.
But here a claim to God's prerogative was voiced, and the reaction was corresponding. Meanwhile, Jesus said exactly what He intended to do and did. The matter is not a simple healing. An ordinary healing can indeed sometimes happen through the prayers of an ordinary person, if that person is righteous. But in such a case the prayer of the righteous person becomes part of the action of God that heals the person. Such healing costs no small spiritual effort, above all, of course, for the one who asks for healing. For in this case God's work is done first of all through him. And in the fallen world it is very difficult to resist the evil of which any illness is a manifestation.
Jesus heals differently. He simply introduces the person into the Kingdom. That is why He tells the one He heals that his sins are forgiven: now, having been joined to the life of the Kingdom and having trusted Jesus, the healed person begins to belong to Him, and from now on he will have to resolve the questions connected with his sinfulness personally with Jesus.
The Savior forgives the healed man's sins as the King of His Kingdom, into which He introduces the person He heals. And there, in the Kingdom, healing happens by itself and much more simply than in the fallen world: there is no place for evil in the Kingdom, and illness there simply disappears by itself. Healing a person despite his nature spoiled by sin is much harder than freeing him from illness by freeing that nature from the power of sin and changing it. Jesus acts precisely in this way, as He says directly to the people around Him. Whether to believe Him or not is for them to decide.