16 And they who usually do so have a grudge against this solemnity of yours; and since because of their envious disposition they cannot endure this solemnity, they hate the cause of it, and go so far in their madness as to deny the merits of the martyrs, whose deeds even the evil spirits confess. But this is not to be wondered at since such is the faithlessness of unbelievers that the confession of the devil is often more easy to endure. For the devil said: “Jesus, Son of the living God, why are You come to torment us before the time?” And the Jews hearing this, even themselves denied Him to be the Son of God. And at this time you have heard the devils crying out, and confessing to the martyrs that they cannot bear their sufferings, and saying, “Why are you come to torment us so severely?” And the Arians say: “These are not martyrs, and they cannot torment the devil, nor deliver any one,” while the torments of the devils are proved by their own words, and the benefits of the martyrs are declared by the restoring of the healed, and the proof of those that are loosed.
Source: Letters (New Advent)