Christ is all in all. – Colossians 3:11.

The Apostle was arguing for holiness. He was earnestly contending against sin and for the maintenance of Christian graces, but he did not, as some do, who would like to be thought preachers of the gospel, resort to reasons inconsistent with the gospel of free grace. He did not bring forward a single legal argument; he did not say, “This do, and ye shall merit reward;” or, “This do not, and ye shall cease to be the beloved of the Lord.” He knew that he was writing to believers, who are not under the law but under grace, and he therefore used arguments fetched from grace, and suitable to the character and condition of “the elect of God, holy and beloved.”

In the new birth we are created in the image of Jesus, the second Adam, and in consequence all the distinctions that appertain to the old creation are rendered valueless; “there is neither Greek nor Jew, circumcision nor uncircumcision, Barbarian, Sythian, bond nor free: but Christ is all, and in all”: the argument from this fact being, that since the only abiding distinction in the new creation is Christ, we should take care that his image is most clearly stamped upon us so that we may not only confess with our tongues that we are Christians, but our conversation and our entire character shall bespeak us to be such. As you may recognize the Jew by his physiognomy, the Greek by his gracefulness, and the barbarian by his uncouthness; so should the Christian be known by his Christliness, by the light, love, and life of Christ streaming forth from him. This is the seal of God which is set upon the forehead of the faithful, and this is the mark of election which is in due season graven in the right hand of all the elect.~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1006.cfm