Romans 6:16
Do you not know that if you present yourselves to anyone as obedient servants you are his (voluntary) servants because you obey him? This could be obedience to sin with death in view or obedience to righteousness with holiness in view?
John 8:34
Jesus answered: Truly I tell you every one who commits sin is a slave of sin.
2 Peter 2:19
They promise them freedom, while they are bondservants of corruption. A man is brought into bondage by one and enslaved by another.
Matthew 6:24
You cannot serve two masters. You will hate one and love the other. You will be loyal to one master and despise the other. You cannot serve both God and money (wealth) (material possessions).
Joshua 24:15
If you are not willing to serve him, decide today whom you will serve, the gods your ancestors worshiped in Mesopotamia or the gods of the Amorites, in whose land you are now living. As for my family and me, we will serve Jehovah.'
Romans 6:12-13
Let no sin rule in your mortal body, that you should obey the lustful desires.
Romans 6:17
But thanks to God, that you were the servants of sin yet you became obedient from the heart to the teachings delivered to you.
Romans 6:19-23
I speak in human terms because of the weakness of your flesh. You once presented your members as servants to uncleanness and to sin. Now you present your members as servants to righteousness and sanctification (purification) (holiness).