Jamieson, Fausset and Brown on Acts 9:4-6

4-6. he fell to the earth--and his companions with him (Ac 26:14), who "saw the light" (Ac 22:9).

and heard a voice saying unto him--"in the Hebrew tongue" (Ac 26:14).

Saul, Saul--a reduplication full of tenderness [De Wette]. Though his name was soon changed into "Paul," we find him, in both his own narratives of the scene, after the lapse of so many years, retaining the original form, as not daring to alter, in the smallest detail, the overpowering words addressed to him.

why persecutest thou me?--No language can express the affecting character of this question, addressed from the right hand of the Majesty on high to an infuriated, persecuting mortal. (See Mt 25:45, and that whole judgment scene).