Jamieson, Fausset and Brown on Acts 13:33

33. God hath fulfilled the same--"hath completely fulfilled."

in that he hath raised up Jesus again--literally, "raised up"; but the meaning is (notwithstanding the contrary opinion of many excellent interpreters) "from the dead"; as the context plainly shows.

as it is written in the second psalm--in many manuscripts "the first Psalm"; what we call the first being regarded by the ancient Jews as only an introduction to the Psalter, which was considered to begin with the second.

this day have I begotten thee--As the apostle in Ro 1:4 regards the resurrection of Christ merely as the manifestation of a prior Sonship, which he afterwards (Ac 8:32) represents as essential, it is plain that this is his meaning here. (Such declarative meaning of the verb "to be" is familiar to every reader of the Bible). See Joh 15:8, "So shall ye be," that is, be seen to be "My disciples." It is against the whole sense of the New Testament to ascribe the origin of Christ's Sonship to His resurrection.