Often the Bible is straightforward regarding why actions are taken. The lesson from these actions often explain other parts of the Bible.
Matthew 9:1-8 is such a passage:
Getting into a boat, Jesus crossed over the Sea of Galilee and came to His own city. And they brought to Him a paralyzed man lying on a stretcher. And seeing their faith, Jesus said to the man who was paralyzed, “Take courage, son; your sins are forgiven.” And some of the scribes said to themselves, “This man is blaspheming!” And Jesus, perceiving their thoughts, said, “Why are you thinking evil in your hearts? For which is easier, to say, ‘Your sins are forgiven,’ or to say, ‘Get up and walk’? But so that you may know that the Son of Man has authority on earth to forgive sins”—then He *said to the paralyzed man, “Get up, pick up your stretcher and go home.” And he got up and went home. But when the crowds saw this, they were awestruck, and they glorified God, who had given such authority to men.
Verse 6 is the point of the action Jesus takes: ‘”But so that you may know that the Son of Man has authority on earth to forgive sins”—then He *said to the paralyzed man, “Get up, pick up your stretcher and go home.”’
Hence one reason Jesus heals throughout the Gospels is to show He has the power to forgive sins. Thus when He arrives at the day of atonement the disciples who would have seen and heard Him heal and teach should have understood what He was accomplishing and then when He commanded them to preach repentance and forgiveness of sins in His name to the nations (Luke 24:45-48) they would have believed Him.
Jesus tells and demonstrates to everyone throughout His ministry His ultimate aim which is to be the source of our knowledge of God and reconciliation with Him through the forgiveness of our sins. These verses in Matthew tell us that whenever we read of Jesus healing He is telling us that in part His goal is to begin, develop and increase our faith in His ability to forgive us of our sins.