As he drew near to Jericho, a blind man was sitting by the roadside begging; and hearing a multitude going by, he inquired what this meant. They told him, "Jesus of Nazareth is passing by."
And he cried, "Jesus, Son of David, have mercy on me!" And those who were in front rebuked him, telling him to be silent; but he cried out all the more, "Son of David, have mercy on me!" And Jesus stopped, and commanded him to be brought to him; and when he came near, he asked him, "What do you want me to do for you?" He said, "Lord, let me receive my sight." And Jesus said to him, "Receive your sight; your faith has made you well." And immediately he received his sight and followed him, glorifying God; and all the people, when the saw it, gave praise to God.
Luke 18:35-43
The blind man's faith was very strong. He knew with out even seeing Jesus, that he was the Son of man. For he asked Jesus not for his sight, at first, but mercy. Verse 38: And he cried "Jesus, Son of David, have mercy on me!" and again in verse 39. Notice how he addresses Jesus, "Lord, let me receive me sight." He knew that Jesus was Lord, as I said before. Jesus and God saw his faith, and for this he received his sight. Verse 42 says, And Jesus said to him, "Receive your sight; your faith has made you well." It is his faith, and following of the Lord that heals him. For he truly believed, and knew that Jesus could heal him.
