Adam Clarke on 1 Corinthians 7:22

For he that is called - The man who, being a slave, is converted to the Christian faith, is the Lord's freeman; his condition as a slave does not vitiate any of the privileges to which he is entitled as a Christian: on the other hand, all free men, who receive the grace of Christ, must consider themselves the slaves of the Lord, i.e. his real property, to be employed and disposed of according to his godly wisdom, who, notwithstanding their state of subjection, will find the service of their Master to be perfect freedom.