Charles Spurgeon Commentary John 5:14

"Afterward Jesus findeth him in the temple, and said unto him, Behold, thou art made whole: sin no more, lest a worse thing befall thee." — John 5:14 (ASV)

Probably, this man's illness had been caused by sin. Christ bids him to keep clear of sin from now on, so that a worse calamity would not come upon him.