What did David prophesy about in the Psalms Peter quotes in Acts 2?
David spoke prophetically in the Psalms about Christ's coming, death, and resurrection. This was not yet about salvation for Gentiles, but so all things could be fulfilled for Him to be Israel's Redeemer, and for Israel to pass it out to surrounding nations and serve as priests.
Les explains that the Acts 2 setting is the day of Pentecost, seven weeks later, and the message is addressed to Ye men of Israel—nothing is said concerning the Gentiles. Jesus of Nazareth was approved by God through miracles, wonders, and signs to prove He was the promised Messiah and King, ready to give Israel the kingdom, as well as to be their Redeemer. Then, in the verses between Acts 2:25 and 30, the speaker goes back into the Psalms and quotes David. David speaks prophetically concerning Christ's coming, death, and resurrection. But this prophecy is not yet about the salvation of Gentiles; it is only that everything could be fulfilled so He could be the Redeemer of Israel, and Israel could pass it out to the nations around them and be priests.
For David speaketh concerning him, I foresaw the Lord always before my face, for he is on my right hand, that I should not be moved:
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