I have seen folly... — Literally, as in Job 6:6, that which is unsavoury — i.e., insipid, and so, ethically, foolish. The guilt of the prophets of Samaria cannot be passed over, but it is noticed, as in Jeremiah 3:6-10, only in order to compare it with the darker evils of those of Judah and Jerusalem.
They prophesied in Baal. — i.e., in the name and as if by the power of Baal. Comp. 1 Kings 18:19; 1 Kings 22:6-7.