From: Mark 8:22-26
The Curing of a Blind Man at Bethsaida
 And they came to Bethsaida. And some people brought to Him (Jesus) a blind man, and begged Him to touch him.  And He took the blind man by the hand, and led him out of the village. And when He had spit on his eyes and laid His hands upon him, He asked, "Do you see anything?"  And he looked up and said, "I see men, but they look like trees, walking."  Then again He laid His hands upon his eyes; and He looked intently and was restored, and saw everything clearly.  And He sent him away to his home, saying, "Do not even enter the village."
22-25. Normally the cures which Jesus worked were instantaneous; not so in this case. Why? Because the blind man's faith was very weak, it would seem, to begin with. Before curing the eyes of his body, Jesus wanted the man's faith to grow; the more it grew and the more trusting the man became, the more sight Jesus gave him. In this way Jesus acted in keeping with His usual pattern: not working miracles unless there was a right predisposition, yet encouraging a good disposition in the person and giving more grace as he responds to the grace already given.
God's grace is essential even for desiring holy things: "Give us light, Lord. Behold, we need it more than the man who was blind from his birth, for he wished to see the light and could not, whereas nowadays, Lord, no one wishes to see it. Oh, what a hopeless ill is this! Here, my God, must be manifested Thy power and Thy mercy" (St. Teresa, "Exclamations of the Soul to God", 8).
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.