Now that he ascended - That is, it is affirmed in the Psalm that he “ascended” - “Thou hast ascended on high.” This implies that there must have been a previous “descent;” or, as applicable to the Messiah, “it is a truth that he previously descended.” It is by no means certain that Paul meant to say that the “word” “ascended” demonstrated that there must have been a previous descent; but he probably means that in the case of Christ there was, “in fact,” a descent into the lower parts of the earth first. The language used here will appropriately express his descent to earth.
Into the lower parts of the earth - To the lowest state of humiliation. This seems to be the fair meaning of the words. Heaven stands opposed to earth. One is above; the other is beneath. From the one Christ descended to the other; and he came not only to the earth, but he stooped to the most humble condition of humanity here; see Philippians 2:6-8; compare notes on Isaiah 44:23. Some have understood this of the grave; others of the region of departed spirits; but these interpretations do not seem to be necessary. It is the “earth itself” that stands in contrast with the heavens; and the idea is, that the Redeemer descended from his lofty eminence in heaven, and became a man of humble rank and condition; compare Psalms 139:15.