the flame went up. See note on Genesis 4:4.
the altar. The rock is deemed the altar.
Related Commentaries of Judges 13:20
Judges 13:20
20 For it came to pass, when the flame went up toward heaven from off the altar, that the angel of the LORD ascended in the flame of the altar. And Manoah and his wife looked on it, and fell on their faces to the ground.