Col 3:15 And let the peace of Christ arbitrate in your hearts, to which also you were called in one Body; and be thankful. Eph 2:15 ...that He might create the two in Himself into one new man, so making peace.
After Paul wrote concerning the all-inclusive Christ and concerning the new man in whom Christ is all and in all and where there is no room for Greek, Jew, or other cultural distinctions [vs. 3:10,11] , he charged the saints to care for the peace of Christ. Within us we all have something called the peace of Christ.
This is the peace about which Paul speaks in Ephesians 2:15, where we are told that in Himself Christ created one new man out of two peoples. By creating the Jews and the Gentiles into one new man, Christ has made peace. This is the very peace in Colossians 3:15.
Believers with different cultural backgrounds and nationalities have been created into one new man. The oneness of the new man produces genuine peace. Apart from Christ and the church, those of different races and nationalities cannot be truly one.
We are in the new man, where there is no Greek, Jew, circumcision, or uncircumcision. In the new man there are no different races, classes, or nationalities. Rather, there is oneness because Christ is all and in all.
This oneness is our peace. The peace of Christ in Colossians 3:15 is simply the peaceful oneness in the new man.