Thou art my Son, this day have I begotten thee — It is true, he was the Son of God from eternity. The meaning therefore is, I have this day declared thee to be my Son. As St. Paul elsewhere, declared to be the Son of God with power, by the resurrection from the dead, Romans 1:4. And it is with peculiar propriety and beauty that God is said to have begotten him, on the day when he raised him from the dead, as he seemed then to be born out of the earth anew. Psalms 2:7.
Related Commentaries of Acts 13:33
Acts 13:33
33 God hath fulfilled the same unto us their children, in that he hath raised up Jesus again; as it is also written in the second psalm, Thou art my Son, this day have I begotten thee.