Albert Barnes Commentary 1 Kings 18:28

"And they cried aloud, and cut themselves after their manner with knives and lances, till the blood gushed out upon them." — 1 Kings 18:28 (ASV)

Elijah’s scorn roused the priests of Baal to greater exertions. Finally, when the frenzy reached its height, they drew knives, and blood gushed forth from hundreds of self-inflicted wounds. An ecstasy of enthusiasm seized many, and they poured out incoherent phrases or perhaps an unintelligible jargon, which was believed to be a form of divine inspiration and one of their methods of prophecy.

The practice of inflicting gashes on their limbs during their religious exercises was common among the Carians, Syrians, and Phrygians. We can regard it as a modification of the idea of human sacrifice, as the gods were thought to be pleased with the shedding of human blood.

Lancets. The translators likely did not intend the word “lancets” in its modern sense. The Hebrew word is always translated elsewhere as “spears” or “lances,” and that is probably its meaning here.