" Paul's favorite description of himself was doulos, which means "slave"-one purchased for service. He said the same status applies to all believers, for we all have been "bought at a price" (1 Cor. 6:20). We belong to the one who has paid for us in order to redeem us, and now we are called to serve Him. "

― R.C. Sproul , Five Things Every Christian Needs to Grow