Romans 6:20

For when ye were servants of sin, ye were free in regard of righteousness.

This is a reason predicated upon what people themselves recognize as proper and correct, to the effect that the servant of one master is not expected to obey the commands of another. Whereas the disciples were formerly slaves of sin, and were at that time regarded as free of performing any righteous duty; just so, now the disciple is a slave of a new master, Christ; and it would be an incongruous thing, wholly abhorrent and repugnant to a sense of what is right and proper, for the Christian to serve the old master through commital of sin.