Tertullian, Apology 36
If that is how things stand—if the ones discovered as enemies are the very people who were called Romans—why are we, who are considered enemies, denied the name Roman? We cannot be Romans and not be enemies at the same time, since enemies turn up among those who were regarded as Romans. So the piety, religion, and loyalty owed to the emperors does not consist in duties of that sort, by which hostility itself can serve as a veil; it consists in the kind of character through which true citizenship toward the emperor must be shown just as truly as toward everyone else. After all, these works of a good mind are not owed by us to the emperors alone. We do no good deed with an exception for persons, because we do it for the One who does not seek the cost of praise or reward from any human being, but from God, the exactor and rewarder of impartial kindness. We are the same toward the emperors as we are toward our neighbors. For to wish evil, to do evil, to speak evil, to think evil of anyone is equally forbidden to us. Whatever is not permitted against the emperor is not permitted against anyone either; what is not permitted against anyone is, perhaps even more so, not permitted against the one who is so great through God.
Latin
Si haec ita sunt, ut hostes deprehendantur, qui Romani vocabantur, cur nos, qui hostes existimamur, Romani negamur? non possumus et Romani esse, et hostes non esse, cum hostes reperiantur qui Romani habebantur. Adeo pietas et religio et fides imperatoribus dedita non in hujusmodi officiis consistit, quibus et hostilitas magis ad velamentum sui potest fungi, sed in iis moribus, quibus civilitas in imperatorem tam vere, quam circa omnes necesse habet exhiberi. Neque enim haec opera bonae mentis solis imperatoribus debentur a nobis. Nullum bonum sub exceptione personarum administramus, quia nobis praestamus, qui non ab homine aut laudis, aut praemii expensum captamus: sed a Deo exactore et remuneratore indifferentis benignitatis. Iidem sumus imperatoribus, qui et vicinis nostris. Male enim velle, male facere, male dicere, male cogitare de quoquam ex aequo vetamur. Quodcunque non licet in imperatorem, id nec in quemquam, quod in neminem, eo forsitan magis nec in ipsum, qui per Deum tantus est.