"Now as Jesus passed by, He saw a man who was blind from birth.  And His disciples asked Him, saying, 'Rabbi, who sinned, this man or his parents, that he was born blind?'

"Jesus answered, 'Neither this man nor his parents sinned, but that the works of God should be revealed in him.'"

In this case, Jesus healed this man.  Sometimes people are born with physical or mental handicaps who do not get healed of their handicaps in this life.  But God can still be glorified in their lives by the way they live and deal with their handicaps.  There are many promises in the Bible of a better day to come for all who put their trust in God and live to glorify Him regardless of their circumstances in life.