Romans 6:16 explains the principle of slavery to sin or obedience—directly reinforcing the state of being slaves of sin in 6:20.

Romans 6:17 contrasts the past slavery to sin with present obedience from the heart—highlighting the transformation from the state in 6:20.

Romans 6:18 states being set free from sin to become slaves of righteousness—the exact opposite of the condition in 6:20.

John 8:34 states everyone practicing sin is a slave to sin—confirming the same universal truth that being a slave of sin means freedom from righteousness.

Colossians 3:7 recalls the past way of life—paralleling the former state of being slaves of sin in Romans 6:20.