The Jewish leaders were spiritually blind. Although they thought of themselves as teachers, they were unable to understand God's truth. (See: [[rc://en/ta/man/jit/figs-metaphor]])
Jesus uses this question to rebuke the Pharisees for treating the gift as if it were more important than the altar. Alternate translation: "The altar that makes the gift holy is greater than the gift!" (See: [[rc://en/ta/man/jit/figs-rquestion]])