Jesus asks them to confirm their faith in his healing power.
Matthew 9:28-30 When he had gone indoors, the blind men came to him, and he asked them, "Do you believe that I am able to do this?" "Yes, Lord," they replied.  Then he touched their eyes and said, "According to your faith will it be done to you";  and their sight was restored.
Jesus couldn't do any healing in his own home town. Why not? Because they didn't have faith in him.
22 Everyone said good things about him. They were amazed at the gracious words they heard from his lips. "Isn't this Joseph's son?" they asked.
23 Jesus said, "Here is a saying you will certainly apply to me. 'Doctor, heal yourself! Do the things here in your hometown that we heard you did in Capernaum.' "
24 "What I'm about to tell you is true," he continued. "A prophet is not accepted in his hometown. 25 I tell you for sure that there were many widows in Israel in the days of Elijah. And there had been no rain for three and a half years. There wasn't enough food to eat anywhere in the land. 26 But Elijah was not sent to any of those widows. Instead, he was sent to a widow in Zarephath near Sidon. 27 And there were many in Israel who had skin diseases in the days of Elisha the prophet. But not one of them was healed except Naaman the Syrian."
28 All the people in the synagogue were very angry when they heard that
But Jesus said to them, "A prophet is not without honor except in his own country and in his own house." 58 Now He did not do many mighty works there because of their unbelief.
Jesus tells them their faith, and the measure of their faith, has made them whole.
Matthew 9:20-22, 27-30a (KJV) And, behold, a woman, which was diseased with an issue of blood twelve years, came behind him, and touched the hem of his garment: For she said within herself, If I may but touch his garment, I shall be whole. But Jesus turned him about, and when he saw her, he said, Daughter, be of good comfort; thy faith hath made thee whole. And the woman was made whole from that hour....  And when Jesus departed thence, two blind men followed him, crying, and saying, Thou Son of David, have mercy on us. And when he was come into the house, the blind men came to him: and Jesus saith unto them, Believe ye that I am able to do this? They said unto him, Yea, Lord. Then touched he their eyes, saying, According to your faith be it unto you. And their eyes were opened.
Our faith, which is in Jesus and comes through Jesus, heals us.
Acts 3:16 By faith in the name of JESUS, this man whom you see and know was made strong. It is JESUS' name and the faith that comes through HIM that has given this complete healing to him, as you can all see.