9:1 And as Jesus passed by, he saw a man which was blind from his birth.
9:2 And his disciples asked him, saying, Master, who did sin, this man, or his parents, that he was born blind?
9:3 Jesus answered, Neither hath this man sinned, nor his parents: but that the works of God should be made manifest in him.
The disciples ask Jesus about the cause of a man's blindness. Was it because he or his parents sinned? Jesus said neither had sinned. The man was born blind so that Jesus could show off his powers by curing him of his blindness.
9:6 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,
Jesus spits on the ground, mixes his spit with the dirt, and rubs the muddy spit on (or in?) a blind man's eyes.
What a cool way to heal someone. Jesus makes up all these clever, different, stupid ways of healing.
This is slightly different in the inerrent book of Mark 8:22-25 where Jesus takes him out of town and just spits in his eye directly - no mud.