Albert Barnes on Matthew 22:35

A Lawyer. This does not mean one that practised law, as among us; but one learned or skilled in the law of Moses. Mark calls him "one of the scribes." This means the same thing. The scribes were men of learning; particularly men skilled in the law of Moses. He had heard him reasoning with the Sadducees, and perceived that he answered them well; and he was thought to be better qualified to hold a debate with him, (Mark.) This man was probably of a candid turn of mind; perhaps willing to know the truth; and not entering very fully into their malicious intentions, but acting as their agent, Mk 12:34.

Tempting him. Trying him. Proposing a question to test his knowledge of the law.

(i) "one of them" Lk 10:25