John Gill Commentary 1 Kings 18:15

"And Elijah said, As Jehovah of hosts liveth, before whom I stand, I will surely show myself unto him to-day." — 1 Kings 18:15 (ASV)

And Elijah said, as the Lord of hosts lives, before whom I
stand
In whose presence he was, and whose prophet and minister he was; he takes this oath, to assure Obadiah that he would certainly be upon the spot, or to be found, and not expose him to any danger: I will surely show myself unto him today ;
he was determined at all events to present himself to him that day.