Charles Ellicott Commentary Matthew 9:4

"And Jesus knowing their thoughts said, Wherefore think ye evil in your hearts?" — Matthew 9:4 (ASV)

Knowing their thoughts — The better manuscripts read “seeing,” as if by an immediate act of intuition. St. Mark adds his usual “immediately,” and both he and St. Luke use the word that implies full knowledge.

Why do you think evil? — Literally, evil things. The thoughts were evil because, in the face of the mighty works and divine wisdom of the Teacher, they were assuming He had wantonly spoken words that involved the most extreme form of sin against the God in whose name He taught.