Charles Ellicott Commentary Matthew 21:23

"And when he was come into the temple, the chief priests and the elders of the people came unto him as he was teaching, and said, By what authority doest thou these things? and who gave thee this authority?" — Matthew 21:23 (ASV)

The chief priests and the elders—Saint Matthew and Saint Luke add “the scribes,” thus including representatives of the three constituent elements of the Sanhedrin. The character of the teaching is further specified by Saint Luke, who notes that Jesus was “preaching the gospel”—that is, proclaiming the good news of the kingdom, the forgiveness of sins, and the law of righteousness.

Their question—“By what authority...?”—was pointed. As a rule, the right to be an instructor was conferred by the scribes, or their chief representative, on someone who had studied “at the feet” of a great teacher. This person would then be solemnly admitted to that office, an act symbolized by the delivery of a key, which represented the right to interpret.

The question implied that those asking it knew the Prophet of Nazareth had not been admitted in this way. The second question gave force to the first: Could He name the rabbi who had trained or authorized Him to teach?