What does Judges 13:21 mean?
Manoah and his wife knew there was something unusually special about the "man" who told them they would have a son (Judges 13:2–11). Something about the stranger convinced them the message was true, and that He could be trusted. Manoah's wife had called Him a "man of God" who looked like an "angel of God" (Judges 13:6).Before this moment, though, they appear to have had no idea exactly how unusual this "man" was. At His suggestion, and as He stood by, they made an offering to God (Judges 13:12–18). All at once, as they watched (Judges 13:19–20), He suddenly went up into the heavens in the flames burning on the rock altar. Just like that, He disappeared. He was there, then He was gone.
Instantly, Manoah and his wife realized "the man of God" was actually "the angel of the LORD." They now clearly understand that their visitor was God, Himself, in a temporary human form. Their response was entirely appropriate: to fall on their faces in humble worship. This is followed, though, by great fear; Manoah worries they will die since they've "seen" God (Judges 13:22).