John Gill Commentary 1 Kings 18:37

"Hear me, O Jehovah, hear me, that this people may know that thou, Jehovah, art God, and [that] thou hast turned their heart back again." — 1 Kings 18:37 (ASV)

Hear me, O Lord, hear me ;
&c.] Which repetition is made to express his importunity, and the vehement earnest desire of his soul to be heard in such a case, which so much concerned the glory of God.

The Targum is, ``receive my prayer, O Lord, concerning the fire, receive my prayer concerning the rain;'' as if the one respected the sending down the fire on the sacrifice, and the other sending rain on the earth; and which sense is followed by other Jewish writers.

that this people may know that thou art the Lord God ;
and not Baal, or any other idol:

and that thou hast turned their heart back again ;
from idolatry, to the worship of the true God; though some understand this of God's giving them up to a spirit of error, and suffering them to fall into idolatry, and hardening their hearts, as he did Pharaoh's; but the former sense is best.