Charles Ellicott Commentary Acts 13:33

"that God hath fulfilled the same unto our children, in that he raised up Jesus; as also it is written in the second psalm, Thou art my Son, this day have I begotten thee." — Acts 13:33 (ASV)

God hath fulfilled the same unto us their children.—The better manuscripts give, with hardly an exception, unto our children, and the Received text must be regarded as having been modified to achieve what seemed a more natural meaning. Saint Paul’s language, however, is only an echo of Saint Peter’s to us and to our children, in Acts 2:39.

As it is also written in the second psalm.—The variant reading, “in the first Psalm,” given by some manuscripts, is interesting, as it shows that in some copies of the Old Testament, what is now the first Psalm was treated as a kind of prelude to the whole book, the numeration beginning with what is now the second.

Thou art my Son, this day have I begotten thee.—Historically, Psalms 2 appears as a triumph-song, written to celebrate the victory of a king of Israel or Judah—David, Solomon, or another—over his enemies. The king had been shown by that day of victory to be the chosen son of God—the day itself was a new begetting, manifesting the sonship.

So, in the higher fulfillment which Saint Paul finds in Christ, he refers the words, not primarily to the Eternal Generation of the Son of God (“begotten before all worlds”), nor to the Incarnation, but to the day of victory over rulers and priests, over principalities and powers, over death and Hades. The Resurrection manifested in the antitype, as the victory had done in the type, a pre-existing sonship; but it was for those who witnessed it, or heard of it, the ground on which their faith in that sonship rested. Christ was to them the firstborn of every creature, because He was also the firstborn from the dead. (See notes on Colossians 1:15; Colossians 1:18.)