9 (Now this, “He ascended”—what does it mean but that He also first descended into the lower parts of the earth?
Verses 9 to 11 give a commentary on the words “ascended” ( 9-10) and “gave” (11). Verses 9 and 10 are a parenthesis that explains what he just said in the previous verse.
Christ obtained the right to give gifts by His death, burial, resurrection, and ascension.
An ascent presumes a previous descent to earth by Christ. His ascent here is from earth to heaven (Ac 1:9-11). His ascent indicates His victory over sin, Satan, and death (Php 2:5-11).
what does it mean [imply]
The meaning of Christ’s ascension cannot be anything else than that He first descended to earth in His incarnation and death.
but that He also first descended into the lower parts of [belonging to] the earth?
Jesus descended into the grave before He ascended to heaven (Ps 63:9). His death gave victory over sin.
Jesus of the New Testament is the same as Jehovah of the Old Testament.
The obvious purpose of the quotation is to show how Psalm 68 applies to Christ (Jn 3:13; 6:38; 8:14). The reference in Psalm 68 talks about Jehovah, and the Ephesians passage references Christ, showing that Jesus is Jehovah or very God Himself.