Charles Ellicott Commentary Judges 13:20

"For it came to pass, when the flame went up toward heaven from off the altar, that the angel of Jehovah ascended in the flame of the altar: and Manoah and his wife looked on; and they fell on their faces to the ground." — Judges 13:20 (ASV)

From the altar. —The rock (tsor) of Judges 13:19 is now hallowed into an altar (mizbeach).

Fell on their faces. —Compare Leviticus 9:24; Numbers 14:5; Ezekiel 1:28.