And as concerning that he raised him up from the dead, now no more to return to corruption, he said on this wise, I will give you the sure mercies of David. No more to return to corruption - To the grave, to death, the place and state of corruption; for so we should understand the word διαφθοραν in the text.
The sure mercies of David - Τα ὁσια Δαβιδ τα πιϚα. These words are quoted literatim from the Septuagint version of Isaiah 55:3; where the Hebrew is חסדי דוד הנאמנים chasdey David ha-neemanim, of which the Greek is a faithful translation; and which sure mercies of David St. Paul considers as being fulfilled in the resurrection of Christ. From this application of the words, it is evident that the apostle considered the word David as signifying the Messiah; and then the sure or faithful mercies, being such as relate to the new covenant, and the various blessings promised in it, are evidently those which are sealed and confirmed to mankind by the resurrection of Christ; and it is in this way that the apostle applies them. Had there not been the fullest proof of the resurrection of Christ, not one of the promises of the new covenant could have been considered as sure or faithful. If he did not rise from the dead, then, as said the apostle, your faith and our preaching are vain, 1 Corinthians 15:14.
The following observations of Bp. Pearce are judicious: "For the sense of these words, we must have recourse to what God said to David in 2 Samuel 7:11, 2 Samuel 7:12, etc., explained by what is said in Psalms 89:3, Psalms 89:4, Psalms 89:28, Psalms 89:29, Psalms 89:36, where frequent mention is made of a covenant established by God with David, and sworn to by God, that David's seed should endure for ever, and his throne as the days of heaven, and as the sun, to all generations. This covenant and this oath are the sure and sacred things of which Isaiah, Isaiah 55:3, speaks; and Luke in this place. And Paul understood them as relating to the kingdom of Jesus, (the Son of David), which was to be an everlasting kingdom; and if an everlasting one, then it was necessary that Jesus should have been (as he was) raised from the dead; and, to support this argument, Paul, in the next verse, strengthens it with another, drawn from Psalms 16:10."