Albert Barnes Commentary 1 Kings 18:19

"Now therefore send, and gather to me all Israel unto mount Carmel, and the prophets of Baal four hundred and fifty, and the prophets of the Asherah four hundred, that eat at Jezebel`s table." — 1 Kings 18:19 (ASV)

The prophet chose Carmel as the location for the gathering to which he invited, or rather summoned, King Ahab (see note on Joshua 12:22). Its thick jungles of shrubs, dwarf oaks, and olive trees would provide abundant wood for the intended sacrifice. The site also had a perennial spring and an ancient "altar of the LORD" (1 Kings 18:30), which likely belonged to the earlier era of non-idolatrous high-place worship—perhaps even a structure built by one of the patriarchs.

The location was strategically chosen. On one side, it offered a view of the Mediterranean Sea, from where the first sign of rain would likely appear. On the other side was Jezreel, the royal residence at that time, with its palace and idol temples. This ensured the contest would take place, so to speak, in full view of the proud queen and her minions.

The prophets of Baal — The priests of Baal are called "prophets" not primarily because they claimed to foretell the future, but because they were teachers of a false religion. More specifically, they are given this title because they stand in opposition to the "prophet of the LORD," with whom they were about to compete.

The prophets of the groves, four hundred — This should be translated as "of the grove" (singular). These were the prophets, or priests, associated with the sacred pole—the Asherah (אשׁרה 'ăshêrāh)—that Ahab had erected, likely in Jezreel (see 1 Kings 16:33). The number 400 seems to have been one particularly favored by Ahab, as we find 400 prophets again at the end of his reign (1 Kings 22:6). The number 40 was also significant in the religious system of the Jews (1 Kings 6:17; Exodus 26:19; Deuteronomy 25:3; Ezekiel 41:2).

Which eat at Jezebel’s table — This phrase should be understood as "which eat from Jezebel’s table." Royal etiquette would not have allowed them to eat at the queen's table itself, which was set in the women's quarters of the palace. Instead, they were fed from the surplus of her daily provisions, which were undoubtedly on a lavish scale (Compare 1 Kings 4:22–23).