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, Art thou that my lord Elijah? And as Obadiah was in the way, behold, Elijah met him: and he knew him, and fell on his face, and said, Art thou that my lord Elijah?
The meeting takes place on the way, while Obadiah is out searching for pasture during the famine and drought in Samaria. As they meet, Obadiah recognizes Elijah, falls on his face before him in respect and reverence, and addresses him as his lord Elijah, God's prophet.
This belongs to the account of Elijah's ministry during Israel's national idolatry and the three-and-a-half-year famine, including his stand on Mount Carmel and the rain that followed, with the meeting placed after the drought and before the rain in his work against idolatry. The meeting between Elijah and Obadiah itself is left unexplained. Obadiah's respectful reverence fits his faithfulness to God during Israel's apostasy, even while serving King Ahab.
The encounter leads Elijah to entrust Obadiah with a message for Ahab that Elijah is there, sending the message through Obadiah rather than going to the king himself. Obadiah is afraid to carry the message because it is dangerous; he fears Ahab will kill him and that Elijah will disappear before he returns. Elijah reassures Obadiah with an oath that he will show himself to Ahab that day. After this period Elijah fled Jezebel's threats, and God appointed another prophet to continue the work.