Matthew 12:38 - Ellicott's Commentary On The Whole Bible

Master, we would see a sign from thee. — The order varies slightly from that in St. Luke, in which the demand for a sign follows on the parable of the unclean spirit returning to his house. In both, however, the sequence of thought appears the same. The tone of authority, as of one who is the judge of all men, leads to the challenge — “Give us a sign by which you may convince us that you have a right thus to speak.”