8. Wherefore--"For which reason," namely, in order to intimate that Christ, the Head of the Church, is the author of all these different gifts, and that giving of them is an act of His "grace" [ESTIUS].
      he saith--God, whose word the Scripture is (Ps 68:18).
      When he ascended--GOD is meant in the Psalm, represented by the ark, which was being brought up to Zion in triumph by David, after that "the Lord had given him rest round about from all his enemies" (2Sa 6:1-7:1; 1Ch 15:1-29). Paul quotes it of CHRIST ascending to heaven, who is therefore GOD.
      captivity--that is, a band of captives. In the Psalm, the captive foes of David. In the antitypical meaning, the foes of Christ the Son of David, the devil, death, the curse, and sin (Col 2:15; 2Pe 2:4), led as it were in triumphal procession as a sign of the destruction of the foe.
      gave gifts unto men--in the Psalm, "received gifts for men," Hebrew, "among men," that is, "thou hast received gifts" to distribute among men. As a conqueror distributes in token of his triumph the spoils of foes as gifts among his people. The impartation of the gifts and graces of the Spirit depended on Christ's ascension (Joh 7:39; 14:12). Paul stops short in the middle of the verse, and does not quote "that the Lord God might dwell among them." This, it is true, is partly fulfilled in Christians being an "habitation of God through the Spirit" (Eph 2:22). But the Psalm (Ps 68:16) refers to "the Lord dwelling in Zion for ever"; the ascension amidst attendant angels, having as its counterpart the second advent amidst "thousands of angels" (Ps 68:17), accompanied by the restoration of Israel (Ps 68:22), the destruction of God's enemies and the resurrection (Ps 68:20, 21, 23), the conversion of the kingdoms of the world to the Lord at Jerusalem (Ps 68:29-34).

JFB.