Christ then, who speaks for their good, not to gratify their vainglory, explains His meaning to have been that they were the servants not of men, but of sin, the hardest kind of servitude, from which God only can rescue: Jesus answered them, Verily, verily, I say unto you, Whosoever committeth sin is the servant of sin.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Hom. liv. 1