John Gill Commentary 1 Kings 18:7

"And as Obadiah was in the way, behold, Elijah met him: and he knew him, and fell on his face, and said, Is it thou, my lord Elijah?" — 1 Kings 18:7 (ASV)

And as Obadiah was in the way. In his district, making his observations:

behold, Elijah met him: where is not said; but he was, no doubt, upon the road from Zarephath to Samaria:

and he knew him; that is, Obadiah knew Elijah, having seen him at Ahab's court before he absconded:

and fell on his face, and said, art thou that my lord Elijah? thus doing him honour and reverence both by words and gesture, as being an extraordinary prophet of the Lord.