The Apostle presents three gospel principles that have bearing on this matter. They relate to the call that gathers people into the kingdom of Christ, the control of their hearts that relates to their character and conduct as His subjects, and a grateful spirit that animates everything.
they had been called
The Apostle reminds the Colossians that they were indeed called into the peace of Christ in one body (Col. 3:15). This is a reference to the Spirit’s call that accompanies the gospel word. There is no mention in Acts of a church’s being formed in Colossae, but the great likelihood is that it was an extension from Ephesus (Acts 19:10) and via the ministry of Epaphras, both there and in nearby Laodicea and Hierapolis (1:7; 4:12–14). Epaphras had preached “the word of truth” to them and they had “understood the grace of God” as the Holy Spirit called them out of “the domain of darkness and transferred [them] to the kingdom of [God’s] beloved Son” (Col. 1:13). Before that, they “were alienated and hostile in mind, doing evil deeds” (v. 21) but became reconciled to God by Christ’s death and so were at peace with God, and He with them (v. 22).
But as each responded to the call of the gospel, they found that others had done so too. They were God’s chosen ones (3:12). A new family was formed—brothers and sisters who believed in Christ, loved each other, and shared the hope of heaven. Regardless of color, caste, or (former) creed, they had as their Father the Father of the Lord Jesus Christ (1:2–3). They were indeed a “called-out body,” each belonging to the other and all belonging to Christ, who is to be “all in all.”
they were to be controlled
By the time that Paul wrote, the verb translated “rule” was no longer used only with regard to umpiring at the Olympic Games but was used also in a general sense of exercising oversight or control of people’s lives. This is to be a matter of the heart's being under control, and in the Bible, “heart” is not the place of feelings alone. Calm and cozy sensations are not to be identified with the control of peace. The heart is the whole person at his source, including his mind and will as well as emotion—“the springs of life” (Prov. 4:23).
Raised to a new life with Christ, every believer is to have his heart oriented toward heaven and conditioned by it more and more (Col. 3:1–4). All that characterized the old self is to be discarded, and what is in accord with the new self—thoughts and desires, words and deeds—is to be renewed (v. 10). This is “keeping the peace” in one’s own spirit and conscience (Phil. 4:4–7) and also with others by compassion, kindness, humility, meekness, patience, and forgiveness toward them (Col. 3: 12–14). It is part of “the fruit of the Spirit” and the antithesis of the “works of the flesh” (Gal. 5:22).
they were to be thankful
This is not unconnected with the rule of peace in the heart. Thanksgiving is referred to often in this letter as a response to God’s graciousness in delivering from bondage (1:13), providing life and strength in Christ (2:7), and animating a worshiping and serving community (3:16–17; 4:2). But more than a command to give thanks is referred to here. “Be thankful” means to become thankful people so that the discontent that breeds contentiousness is banished, and everyone regards the well-being of “the one body” as a paramount concern.