John Calvin Commentary Mark 8:22

"And they come unto Bethsaida. And they bring to him a blind man, and beseech him to touch him." — Mark 8:22 (ASV)

Mark seems to have related this miracle, which the other two Evangelists omit, chiefly because Christ restored sight to the blind man not in an instant, as He usually did, but in a gradual manner. He most probably did this to prove, in this man's case, that He had full liberty in His way of proceeding and was not restricted to a fixed rule, so that He could use a variety of methods in exercising His power.

Therefore, He did not instantly enlighten the eyes of the blind man and make them fully functional; instead, He first gave him a dim and confused perception, and afterwards, by laying His hands on him a second time, enabled him to see perfectly. Thus, the grace of Christ, which had previously been poured out suddenly on others, flowed by drops, so to speak, on this man.