Albert Barnes Commentary 1 Kings 18:29

"And it was so, when midday was past, that they prophesied until the time of the offering of the [evening] oblation; but there was neither voice, nor any to answer, nor any that regarded." — 1 Kings 18:29 (ASV)

And they prophesied - Compare 1 Kings 22:12. The expression seems to be used for any case where words were uttered by people in a state of religious ecstasy.

Until the time of the offering - Rather, “Until toward the time.” Elijah had built his altar by the actual time of the offering (1 Kings 18:36).