(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.

People's New Testament

4:9 Now that he ascended... also descended first. Paul, in applying this to Christ, shows that it implies that he must have descended from heaven, before his ascension to heaven. This must necessarily follow, if the one ascending is divine, and has a home in heaven, as Ps 68:18 indicates.

Wesley's Notes

4:9 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, Psa 139:15; the grave, Psa 63:9.

Jamieson-Fausset-Brown Bible Commentary

9. 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 (Eph 4:8, 17, 18). It must therefore be God the Son (Joh 6:33, 62). As He declares (Joh 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" (Eph 4:10, Greek, "the whole universe of things") may imply the same. But see on [2368]Eph 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 (Ps 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 (Ac 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. Ac 2:27, 28, and Ro 10:7, favor the view of the reference being simply to His descent to Hades. So Pearson in Exposition of the Creed (Php 2:10).

Matthew Henry's Concise Commentary

4:7-16 Unto every believer is given some gift of grace, for their mutual help. All is given as seems best to Christ to bestow upon every one. He received for them, that he might give to them, a large measure of gifts and graces; particularly the gift of the Holy Ghost. Not a mere head knowledge, or bare acknowledging Christ to be the Son of God, but such as brings trust and obedience. There is a fulness in Christ, and a measure of that fulness given in the counsel of God to every believer; but we never come to the perfect measure till we come to heaven. God's children are growing, as long as they are in this world; and the Christian's growth tends to the glory of Christ. The more a man finds himself drawn out to improve in his station, and according to his measure, all that he has received, to the spiritual good of others, he may the more certainly believe that he has the grace of sincere love and charity rooted in his heart.