The flame; either arising from the fire which Manoah brought for the offering, or produced by the angel out of the rock in a miraculous manner.
From off the altar, i.e. from that part of the rock which served instead of an altar, upon which the sacrifice was laid.
The angel ascended in the flame, to manifest his nature and essence to be spiritual, because not capable of hurt by the fire; and celestial.
Fell on their faces; partly in reverence to that glorious presence manifested in so wonderful a manner; and partly out of a religions horror and fear of death upon this occasion, as is expressed Jud_13:22, for the prevention whereof they fell down in way of supplication to God.