Romans 6:16

Obedience— That which he calls here simply obedience, in other places he calls obedience of faith, and obedience of Christ; meaning a reception of the Gospel of Christ. The Apostle explains the obligations of Gentile Christians in their present state, in opposition to the Gentile or heathen state, by the case of slaves, at that time well understood all over the world. A servant or slave was his master's property, a part of his goods, which he might keep for life, sell to another master, or manumit and set free, as he pleased. Consequently the servant must be employed, as the master that he was under was either good or bad; and must fare according as his master happened to be rich or poor, good-natured or churlish, niggardly or liberal: and his being released from a bad master, and put into the hands of a good one, kind and generous, must be a very desirable and happy alteration in his circumstances. See Locke.