Cyprian of Carthage, Epistle 63.4 (Cup of the Lord)
But if an incurable fury persists among the insane, and the blindness that began remains in its own night after the Holy Spirit has departed, our plan will be to separate individual brothers from their deception and set them apart from their contagion so that no one falls into the snares of error. For an offering cannot be sanctified where the Holy Spirit is not, nor can the Lord benefit anyone through the prayers and supplications of one who has himself violated the Lord. If Fortunatianus persists in this fury of his, whether he has forgotten his own crime through the devil's blindness or has become a minister and servant of the devil to deceive the brotherhood, you must strive as much as you can. In this darkness of the raging devil, recall the minds of the brothers from error so that they do not easily consent to alien madness or make themselves participants in the crimes of the desperate, but rather hold fast to the perpetual continuity of their salvation and integrity, which they have preserved and guarded.
Latin
Si vero apud insanos furor insanabilis perseverarit, et, recedente Spiritu sancto, quae coepit caecitas in sua nocte permanserit, consilium nobis erit singulos fratres ab eorum fallacia separare, et, ne quis in laqueos erroris incurrat, ab eorum contagione secernere, quando nec oblatio sanctificari illic possit ubi Spiritus sanctus non sit, nec cuiquam Dominus per ejus orationes et preces prosit qui Dominum ipse violavit. Quod si Fortunatianus, aut immemor criminis sui per diaboli caecitatem, aut minister et servus diabol factus ad decipiendam fraternitatem, in hoc suo furore permanserit, vos quantum potestis elaborate, et in hac caligine diaboli saevientis fratrum mentes ab errore revocate, ne alienae dementiae facile consentiant, ne se desperatorum delictis participes faciant, sed teneant integri salutis suae et integritatis conservatae a se et custoditae perpetuum tenorem.