Paul quotes from Isaiah 55:3. His quotation is from the Septuagint translation of the Hebrew text. Using this quotation, Paul affirms that the blessings which God has promised to David, the blessing of an eternal kingdom (2 Samuel 7:13), is given to Jesus Christ. As a result of his perfect obedience, he is the recipient of this blessing.
34 And as for the fact that he raised him from the dead, no more to return to corruption, he has spoken in this way, “‘I will give you the holy and sure blessings of David.’