Whom they refused - That is, when he first presented himself to them, Exodus 2:13-14. Stephen introduces and dwells upon this refusal in order, perhaps, to remind them that this had been the character of their nation, and to prepare the way for the charge which he intended to bring against those whom he addressed, as being stiff-necked and rebellious. See Acts 7:51-52, etc.
A ruler - A military leader, or a governor in civil matters.
A deliverer - A Redeemer - λυτρωτὴν lutrōtēn. It properly means one who redeems a captive or a prisoner by paying a “price” or “ransom.” It is applied thus to the Lord Jesus, as having redeemed or purchased sinners by his blood as a price, Titus 2:14; 1 Peter 1:18; Hebrews 9:12. It is used here, however, in a more “general” sense to denote “the deliverance,” without specifying the manner. Compare Exodus 6:6; Luke 24:21; Luke 1:68; Luke 2:38.
By the hand of the angel - Under the direction and by the “help” of the angel, Numbers 20:16. See on Acts 7:30.