Albert Barnes 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)

When he was come into the temple. That is, probably, into the inner court; the court of the Israelites. They took this opportunity when he was not surrounded by the multitude.

By what authority, etc. There was a show of propriety in this question. He was making great changes in the affairs of the temple, and they claimed the right to know why this was done, contrary to their permission. He was not a priest; he had no civil or ecclesiastical authority as a Jew. It was sufficient authority indeed, that he came as a prophet, and worked miracles. But they professed not to be satisfied with that.

These things. The things which he had just done, in overturning the seats of those that were engaged in traffic, Matthew 21:12.