Being a slave not only meant belonging to someone else; it also meant being always available to obey that person in every way. The slave’s sole duty was to carry out the master’s wishes, and the faithful slave was eager to do so without hesitation or complaint. After all, “slaves know no law but their master’s word; they have no rights of their own; they are absolute possessions of their master; and they are bound to give their master unquestioning obedience.”

Building on this imagery, the New Testament repeatedly calls believers to faithfully obey the Master. As one author explains:

As Christ is Lord, so the Christian is slave, even bondslave, owing unquestioning obedience. Paul explicitly compares spiritual with literal slavery (e.g. Colossians 3:22-24), speaks of slave-marks and seals of Christ’s possession, and works out in detail the conception of the Christian as purchased, belonging to his Lord: “Ye are not your own, ye are bought with a price.” To be alive at all “means fruitful labor” – the slave exists only to work! (1 Corinthians 6:19, 20, Philippians 1:22) So represented, consecration is complete moral submission to Christ’s absolute claim and ownership.

(from Slave by John MacArthur, p. 46)

~

Slaves, obey in everything those who are your earthly masters, not by way of eye-service, as people-pleasers, but with sincerity of heart, fearing the Lord. Whatever you do, work heartily, as for the Lord and not for men, knowing that from the Lord you will receive the inheritance as your reward. You are serving the Lord Christ.
Colossians 3:22-24

Or do you not know that your body is a temple of the Holy Spirit within you, whom you have from God? You are not your own, for you were bought with a price. So glorify God in your body.
1 Corinthians 6:19, 20

If I am to live in the flesh, that means fruitful labor for me. Yet which I shall choose I cannot tell.
Philippians 1:22