Question:
In Ephesians 4:8-10, what does it mean that Christ descended “into the lower parts of earth?”

Answer:
“The lower parts of the earth” refers to His depths of suffering. Christ speaks in Psalm 40:2 of being taken out of “an horrible pit.”

There is not a place between glory and the cross that Christ has not occupied and conquered and has the remedy for us:
“Sing, O ye heavens; for the LORD hath done it: shout, ye lower parts of the earth: break forth into singing, ye mountains, O forest, and every tree therein: for the LORD hath redeemed Jacob, and glorified himself in Israel” (Isaiah 44:23).
He gives gifts that we may also conquer in whatever place we are in as Ephesians 4:8-16 says: “Therefore He says: “When He ascended on high, He led captivity captive, and gave gifts to men.” (Now this, “He ascended” — what does it mean but that He also first descended into the lower parts of the earth? He who descended is also the One who ascended far above all the heavens, that He might fill all things.) And He Himself gave some to be apostles, some prophets, some evangelists, and some pastors and teachers, for the equipping of the saints for the work of ministry, for the edifying of the body of Christ, till we all come to the unity of the faith and of the knowledge of the Son of God, to a perfect man, to the measure of the stature of the fullness of Christ; that we should no longer be children, tossed to and fro and carried about with every wind of doctrine, by the trickery of men, in the cunning craftiness of deceitful plotting, but, speaking the truth in love, may grow up in all things into Him who is the head — Christ — from whom the whole body, joined and knit together by what every joint supplies, according to the effective working by which every part does its share, causes growth of the body for the edifying of itself in love.”