Below is Pliny's correspondence with Trajan about Christians in Pontus, and Trajan's reply. Mention or comment about Christians by pagans before 300 CE is rare; this is the first of any importance outside of the New Testament. He is inquiring the emperor on how to deal with the problem of Christians refusing to pay homage to the emperor.

Pliny, Letters 10.96-97

Pliny to the Emperor Trajan
It is my practice, my lord, to refer to you all matters concerning which I am in doubt. For who can better give guidance to my hesitation or inform my ignorance? I have never participated in trials of Christians. I therefore do not know what offenses it is the practice to punish or investigate, and to what extent. And I have been not a little hesitant as to whether there should be any distinction on account of age or no difference between the very young and the more mature; whether pardon is to be granted for repentance, or, if a man has once been a Christian, it does him no good to have ceased to be one; whether the name itself, even without offenses, or only the offenses associated with the name are to be punished.
Meanwhile, in the case of those who were denounced to me as Christians, I have observed the following procedure: I interrogated these as to whether they were Christians; those who confessed I interrogated a second and a third time, threatening them with punishment; those who persisted I ordered executed. For I had no doubt that, whatever the nature of their creed, stubbornness and inflexible obstinacy surely deserve to be punished. There were others possessed of the same folly; but because they were Roman citizens, I signed an order for them to be transferred to Rome.

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