Wherefore he saith, When he ascended up on high, he led captivity captive,
and gave gifts unto men. Now that he ascended,
what is it but that he also descended first into the lower parts of the earth?
Ephesians 4:8-9
The context is taken from Psalm 68:17-20: The chariots of God are twenty thousand, even thousands of angels: . . . Thou hast ascended on high, thou hast led captivity captive: . . . our God is the God of salvation; and unto GOD the Lord belong the issues from death.
The psalmist is apparently describing the Lord among His heavenly hosts, riding home as a mighty king returning with the spoils of battle. Evidently this battle prize consisted of His own people who had been held captive in an alien land but who now had been captured from the enemy by the returning King. To do this, the King “ascended up on high,” leading them to His own throne in the heavens.
But first He had to descend to the earth, and then even to “the lower parts of the earth.”
That is exactly what He did when He died on the cross for the sins of these very captives, then, in the Spirit, descended into Hades to set them free.
He returned with the very “keys of hell (hades, which means the grave) and of death” (Revelation 1:18), alive forevermore." ICR