Context: As Jesus and His disciples pass by a blind beggar, the disciples question the cause of the man's infirmity; is it his own sinfulness or that of his parents? Jesus says that the man's blindness is not a result of sin, but that this man's handicap will give Him an opportunity to perform another work of God. Jesus, referring to His time on the earth as the day, says that He must hasten to do the works of the Father because soon there will again be the night, or darkness, referring to the time after His death:
I must work the works of him that sent me, while it is day: the night cometh when no man can work.
As long as I am in the world, I am the light of the world.
When he had thus spoken, he spat on the ground, and made clay of the spittle, and he anointed the eyes of the blind man with the clay.