Therefore the good man, although he is a slave, is free; but the bad man, even if he reigns, is a slave, and that not of one man, but, what is far more grievous, of as many masters as he has vices.

[Proinde bonus etiamsi seruiat, liber est; malus autem etiamsi regnet, seruus est, nec unius hominis, sed, quod est grauius, tot dominorum, quot uitiorum.]

Augustine of Hippo (354-430) Christian church father, philosopher, saint [b. Aurelius Augustinus]

City of God [De Civitate Dei], Book 4, ch. 3 (4.3) (AD 412-416) [ed. Dods (1871)]
    (Source)

See 2 Peter 2:19 "For people are slaves to whatever masters them." The idea of being a slave to vices was also a Stoic belief. Compare to La Bruyere.

(Source (Latin)). Alternate translations:

And therefore he that is good is free though he be a slave, and he that is evil, a slave though he be a king. Nor is he slave to one man, but that which is worst of all, unto as many masters as he affects vices.
[tr. Healey (1610)]

Thus, a good man, though a slave, is free; but a wicked man, though a king, is a slave. For he serves, not one man alone, but, what is worse, as many masters as he as vices.
[tr. Zema/Walsh (1950)]

Hence even if a good man be a slave, he is free; whereas if a wicked man rule, he is a slave -- and a slave not to one man but, what is worse, to as many masters as he has vices.
[tr. Green (Loeb) (1963)]

The good man, though a slave, is free; the wicked, though he reigns, is a slave, and not the slave of a single man, but -- what is far worse -- the slave of as many masters as he has vices.
[tr. Bettenson (1972)]

Therefore the good man is free even if he is a slave, whereas the bad man is a slave even if he reigns: a slave, not to one man, but, what is worse, to as many masters as he has vices.
[tr. Dyson (1998)]

Thus the good person is free, even if a slave, and the evil person is enslaved, even if a ruler -- enslaved not to one master but, what is far worse, to as many masters as he has vices.
[tr. Babcock (2012)]