Albert Barnes Commentary 1 Kings 20:35

"And a certain man of the sons of the prophets said unto his fellow by the word of Jehovah, Smite me, I pray thee. And the man refused to smite him." — 1 Kings 20:35 (ASV)

The sons of the prophets - This expression occurs here for the first time. It refers to the schools or colleges of prophets that existed in several Israelite, and probably Jewish, towns, where young men were regularly educated for the prophetic office. These “schools” first appear in the time of Samuel (1 Samuel 19:20).

There is no distinct evidence that they continued later than the time of Elisha. However, it is, on the whole, most probable that the institution survived the captivity and that the bulk of the “prophets” whose works have come down to us belonged to them. Amos seems to speak as if his case were an exception (Amos 7:14–15).

Said to his neighbor - Rather, this means “to his friend” or “companion”—one who was, like himself, “a prophet’s son,” and who therefore should have perceived that his colleague spoke “in the word of the Lord.”