Sentence begins with genitive absolute again. In a flame of fire in a bush (en plogi puro batou). Horeb in Exodus 3:1 ; but Sinai and Horeb were "probably peaks of one mountain range" (Page), Horeb "the mountain of the dried-up ground," Sinai "the mountain of the thorns." Literally, "in the flame of fire of a bush" (two genitives, puro and batou dependent on plogi, flame). Descriptive genitives as in Exodus 9:15 ; 2 Thessalonians 1:8 . Bato (bush) is the wild acacia (mimosa nilotica). In Exodus 3:20 it is Jehovah who speaks. Hence "angel" here with Stephen is understood to be the Angel of the Presence, the Eternal Logos of the Father, the Angel of Jehovah.