Nobody had ever heard of anyone miraculously healing the blind, but it was a distinguishing mark of the true Messiah (see Isaiah 61:1-2).
BibleGateway: John 9:1-33 ESV Text: John 9:1-33 John 9:1–33 (Listen) Jesus Heals a Man Born Blind 9:1 As he passed by, he saw a man blind from birth. 2 And his disciples asked him, “Rabbi, who sinned, this man or his parents, that he was born blind?” 3 Jesus answered, “It was not that this man sinned, or his parents, but that the works of God might be displayed in him. 4 We must work the works of him who sent me while it…