Paul seems to be arguing that the blessings promised to David have been given to Jesus Christ, and that we can be sure of this because he was resurrected from the dead. David was promised that a king, whose kingdom would never end (2 Samuel 7:13), would come from his line. Since Jesus Christ has been resurrected, he is the one who receives this promised blessing. The holy and sure blessings belong to the holy descendant of David and through him they are shared with all of God’s people (believers in Christ).1
34 Qu'il l'ait ressuscité des morts, de telle sorte qu'il ne retournera pas à la corruption, c'est ce qu'il a déclaré, en disant:Je vous donnerai les grâces saintes promises à David, ces grâces qui sont assurées.