9 For in Him dwells all the fullness of the Godhead bodily;
10 and you are complete in Him, who is the head of all principality and power.
for (v.9) — referring back to the warning in verse 8 — Any system of thought not centered on Christ is wrong.
in Him (v.9) — emphatic
dwells (v.9) = permanent residence — tense indicates continuous action
“Fullness” (v.9) translates the same word which was found earlier in Colossians 1:19. Here it is defined by the addition of the phrase “of the Godhead.” These latter words translate a term found only here in the New Testament, though a similar, but weaker, word (denoting “divine nature”) is found in Romans 1:17. The word employed in the present passage is an abstract term, betokening not just divine qualities and attributes but the very essence of God — “the whole glorious total of what God is, the supreme Nature in its infinite entirety.”
The Gnostic teachers asserted that deity was filtered through a succession of spirit powers (angelic beings). Paul denies this by affirming that the Godhead in “all” its fullness dwells in Christ. It is in Him that God gives a full and complete expression of Himself.
The fullness of the Godhead dwells in Him bodily (v.9), that is, in incarnate fashion. The fullness of Deity resided in the preincarnate Word (cf. John 1:1 ff), but not in bodily fashion. At Bethlehem, however, the Word was clothed with flesh and made God “gloriously tangible and accessible to us.” — Vaughan, pages 72-73.
“Are complete” (v.10) is a participle in the perfect tense. Literally it is, “and you are in Him, having been filled full with the present result that you are in a state of fullness.” Paul says in Ephesians 3:19, “In order that you may be filled with all the fullness of God” Not, ye are made full in Him, but ye are in Him, made full. In Him dwells the fulness; being in Him, ye are filled.” Being fulfilled with a direct reference to the preceding pleroma; “your fulness comes from His fulness; His pleroma (fulness) is transfused into you by virtue of your incorporation in Him.
We must be careful to note that the fulness of God communicated to the saints does not consist of the divine essence which is alone possessed by Deity, but of such qualities as holiness, righteousness, and the like, as in Ephesians 3:19. What Paul means is that in Christ they find the satisfaction of every spiritual want. It therefore follows of itself that they do not need the angelic powers. That Christ is the Head of every principality and power is a further reason why they should not seek them. All they need they have in Christ. — Wuest, page 204.