Paul is quoting from Psalms:

Thou hast ascended on high, thou hast led captivity captive: thou hast received gifts for men; yea, for the rebellious also, that the Lord God might dwell among them. (Psalms 68:18)

We can understand from the fourth chapter of Ephesians and Psalms 68 that the purpose of Christian ministry is to build the Body of Christ, the house of God.

Speaking of the new Jerusalem, the Tabernacle of God:

And I saw no temple therein: for the Lord God Almighty and the Lamb are the temple of it. (Revelation 21:22)

The reason there is no temple in the new Jerusalem, the perfected Church, is that the entire city is the Tabernacle of God. God and the Lamb dwell in unconcealed glory in the personalities of the saints who compose the holy city.

From the standpoint of the saved nations of the earth, the entire new Jerusalem will be one great tabernacle of God. But from the standpoint of God's elect, the members of the Church, who themselves are the holy city, there is no temple of God other than God and the Lamb Themselves. The new covenant has made it possible for all Israel to know the Lord personally.

There are many places of abode, of rest, in the Father's house—as many as there are members of the elect whom God has called to reveal and portray His way, His truth, and His Life to the heavens and the earth.

. . . if it were not so, I would have told you. . . .

If Christ were to remain as the only house of God He would have told us so. In that case the nature of Christianity would be altogether different from what it is.

If God and Christ were to remain external to our personality the demands upon us would be a small fraction of what they are. But because God and Christ are seeking total union with us, desiring to enter us and become one with us and we with Them, our character transformation must be total.

Becoming an eternal part of the Almighty God is the most significant, the most awesome experience imaginable; but it is the natural destiny of man.

If Christ had decided to remain as the only room in the House of God and to keep us forever external to God's Personality, He would have set up His Kingdom on the earth at His first coming.

But Christ has determined to bring people into the relationship to God that He enjoys. Therefore, the Divine grace that He has shed upon the saints has been working for two thousand years in order that He may appear to the world, not only in His isolated Lordship and majesty but also as the Divine Glory abiding in a multitude of transformed and glorified saints.

He has informed us that He must return to the Father in order that we too may be a room in the eternal Temple of God. As soon as these new rooms have been constructed and occupied, Christ will return as the King of Israel, sitting on the Throne of David.

Therefore will he [Christ] give them [the children of Israel] up, until the time that she which travaileth [the Christian Church] hath brought forth [Christ in the saints]: then the remnant of his [Christ's] brethren [God's elect] shall return unto the children of Israel. (Micah 5:3)

To be continued.