The expression "kingdom of God" must be taken in its context to decide just what the Spirit of God has before Him in the passage of Scripture in which it is found.
We have the setting up of the kingdom of God in its heavenly aspect in Luke 13:28, and in its earthly aspect in Mark 15:43; also Luke 17:20;19:11;21:31.
We have its moral character in Rom. 14:17. This moral character. that began so blessedly at Pentecost has become corrupt. This the Lord alludes to in Luke 13:20,21.
In its true character one must be "born main" to enter it. (John 3:5.)
Paul preached the "kingdom of God"; that is, Paul preached the moral character of the kingdom, exhorting those who believed the gospel to walk worthy of God who had called them to His kingdom and glory. (1 Thess. 2:12.)
The eternal state will witness its true character in full display. "God all in all" means that the true character of God will be seen in the whole of new creation.
How blessed and glorious that eternity of rest!
"Seeing then that all these things shall be dissolved, what manner of persons ought ye to be in all holy conversation and godliness." 2 Peter 3:11.
O TEACH us more of Thy blest ways,
Thou holy Lamb of God!
And fix and root us in Thy grace,
As those redeemed by blood.
O tell us often of Thy love,
Of all Thy grief and pain;
And let our hearts with joy confess
That thence comes all our gain.
For this, O may we freely count-
Whate'er we have but loss;
The dearest object of our love,
Compared with Thee, but dross.
Engrave this deeply on our hearts
With an eternal pen,
That we may, in some small degree,
Return Thy love again.