Jamieson, Fausset and Brown on Psalms 2:7

7. The king thus constituted declares the fundamental law of His kingdom, in the avowal of His Sonship, a relation involving His universal dominion.

this day have I begotten thee--as 2Sa 7:14, "he shall be My son," is a solemn recognition of this relation. The interpretation of this passage to describe the inauguration of Christ as Mediatorial King, by no means impugns the Eternal Sonship of His divine nature. In Ac 13:33, Paul's quotation does not imply an application of this passage to the resurrection; for "raised up" in Ac 13:32 is used as in Ac 2:30; 3:22, &c., to denote bringing Him into being as a man; and not that of resurrection, which it has only when, as in Ac 2:34, allusion is made to His death (Ro 1:4). That passage says He was declared as to His divine nature to be the Son of God, by the resurrection, and only teaches that that event manifested a truth already existing. A similar recognition of His Sonship is introduced in He 5:5, by these ends, and by others in Mt 3:17; 17:5.