and that, he went up, what is it except that he also went down first to the lower parts of the earth?

(Now this, He went up, what is it but that he first went down into the lower parts of the earth?

Now that he has ascended, what is left except for him also to descend, first to the lower parts of the earth?

Now surely this 'going up' must imply that he had already gone down into the world beneath.

Illud autem Ascendit, quid est, nisi quod etiam descenderat prius in inferiores partes terrae?

Now that he ascended. Here again the slanderers exclaim, that Paul's reasoning is trifling and childish. "Why does he attempt to make those words apply to a real ascension of Christ, which were figuratively spoken about a manifestation of the Divine glory? Who does not know that the word ascend is metaphorical? The conclusion, that he also descended first, has therefore no weight." I answer, Paul does not here reason in the manner of a logician, as to what necessarily follows, or may be inferred, from the words of the prophet. He knew that what David spake about God's ascension was metaphorical. But neither can it be denied, that the expression bears a reference to some kind of humiliation on the part of God which had previously existed. It is this humiliation which Paul justly infers from the declaration that God had ascended. And at what time did God descend lower than when Christ emptied himself? ( 'All ' heauton ekenose, Philippians 2:7.) If ever there was a time when, after appearing to lay aside the brightness of his power, God ascended gloriously, it was when Christ was raised from our lowest condition on earth, and received into heavenly glory. Besides, it is not necessary to inquire very carefully into the literal exposition of the Psalm, since Paul merely alludes to the prophet's words, in the same manner as, on another occasion, he accommodates to his own subject a passage taken from the writings of Moses. "The righteousness which is of faith speaketh in this manner, Say not in thine heart, who shall ascend into heaven? (that is, to bring Christ down from above;) or, who shall descend into the deep (that is, to bring up Christ again from the dead.") (Romans 10:6,7 Deuteronomy 30:12.) But the appropriateness of the application which Paul makes of the passage to the person of Christ is not the only ground on which it must be defended. Sufficient evidence is afforded by the Psalm itself, that this ascription of praise relates to Christ's kingdom. Not to mention other reasons which might be urged, it contains a distinct prophecy of the calling of the Gentiles. Into the lower parts of the earth. [1] These words mean nothing more than the condition of the present life. To torture them so as to make them mean purgatory or hell, is exceedingly foolish. The argument taken from the comparative degree, "the lower parts," is quite untenable. A comparison is drawn, not between one part of the earth and another, but between the whole earth and heaven; as if he had said, that from that lofty habitation Christ descended into our deep gulf.

Footnotes

1 - For the lower parts of the earth,' they may possibly signify no more than the place beneath; as when our Savior said, (John 8:23,) Ye are from beneath, I am from above; ye are of this world, I am not of this world;' or as God spake by the prophet, I will shew wonders in heaven above, and signs in the earth beneath.' Nay, they may well refer to his incarnation, according to that of David, (Psalm 139:15,) or to his burial. (Psalm 63:9.)" -- Pearson.

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 Psalm 139:15.

But that he also descended - The meaning of the apostle appears to be this: The person who ascended is the Messiah, and his ascension plainly intimates his descension; that is, his incarnation, humiliation, death, and resurrection.

(Now that he ascended, what is it but that he also descended first into the (h) lower parts of the earth?
(h) Down to the earth, which is the lowest part of the world.

Now that he ascended,.... These words are a conclusion of Christ's descent from heaven, from his ascension thither; for had he not first descended from thence, it could not have been said of him that he ascended; for no man hath ascended to heaven but he that came down from heaven, John 3:13 and they are also an explanation of the sense of the psalmist in the above citation, which takes in his humiliation as well as his exaltation; which humiliation is signified by his descent into the earth:
what is it but that he also descended first into the lower parts of the earth? this the Papists understand of his decent into a place they call Limbus Patrum, which they make to be contiguous to hell; and where they say the patriarchs were detained till Christ's coming; and that he went thither to deliver them out of it; and that these are the captivity he led captive; all which is fictitious and fabulous: for certain it is, that the place where Abraham was with Lazarus in his bosom was not near to hell, but afar off, and that there was a great gulf between them, Luke 16:23 and the spirits or souls of the patriarchs returned to God that gave them, when separated from their bodies, as the souls of men do now, Ecclesiastes 12:7 nor did Christ enter any such feigned place at his death, but went to paradise, where the penitent thief was that day with him; nor were the patriarchs, but the principalities and powers Christ spoiled, the captivity he led captive and triumphed over: some interpret this of Christ's descent into hell, which must be understood not locally, but of his enduring the wrath of God for sin, which was equivalent to the torments of hell, and of his being in the state of the dead; but it may rather design the whole of his humiliation, as his descent from heaven and incarnation in the virgin's womb, where his human nature was curiously wrought in the lowest parts of the earth; and his humbling himself and becoming obedient unto death, even the death of the cross, when he was made sin and a curse for his people, and bore all the punishment due to their transgressions; and his being in Hades, in the state of the dead, in the grave, in the heart of the earth, as Jonah in the whale's belly: reference seems to be had to Psalm 139:15 where "the lower parts of the earth", is interpreted by the Targum on the place of , "his mother's womb"; and so it is by Jarchi, Aben Ezra, Kimchi, and Ben Melec. The Alexandrian copy and the Ethiopic version leave out the word "first" in this clause.

Paul reasons that (assuming Him to be God) His ascent implies a previous descent; and that the language of the Psalm can only refer to Christ, who first descended, then ascended. For God the Father does not ascend or descend. Yet the Psalm plainly refers to God (Ephesians 4:8, Ephesians 4:17-18). It must therefore be GOD THE SON (John 6:33, John 6:62). As He declares (John 3:13), "No man hath ascended up to heaven, but He that came down from heaven." Others, though they did not previously descend, have ascended; but none save Christ can be referred to in the Psalm as having done so; for it is of God it speaks.
lower parts of the earth--The antithesis or contrast to "far above all heavens," is the argument of ALFORD and others, to show that this phrase means more than simply the earth, namely, the regions beneath it, even as He ascended not merely to the visible heavens, but "far above" them. Moreover, His design "that He might fill all things" (Ephesians 4:10, Greek, "the whole universe of things") may imply the same. But see on Ephesians 4:10 on those words. Also the leading "captive" of the "captive hand" ("captivity") of satanic powers, may imply that the warfare reached to their habitation itself (Psalm 63:9). Christ, as Lord of all, took possession first of the earth the unseen world beneath it (some conjecture that the region of the lost is in the central parts of our globe), then of heaven (Acts 2:27-28). However, all we surely know is, that His soul at death descended to Hades, that is, underwent the ordinary condition of departed spirits of men. The leading captive of satanic powers here, is not said to be at His descent, but at His ascension; so that no argument can be drawn from it for a descent to the abodes of Satan. Acts 2:27-28, and Romans 10:7, favor the view of the reference being simply to His descent to Hades. So PEARSON in Exposition of the Creed (Philippians 2:10).

Now this expression, He ascended, what is it, but that he descended - That is, does it not imply, that he descended first? Certainly it does, on the supposition of his being God. Otherwise it would not: since all the saints will ascend to heaven, though none of them descended thence. Into the lower parts of the earth - So the womb is called, Psalm 139:15; the grave, Psalm 63:9.