1 Thessalonians 4:8

"And grieve not," he adds, "the Holy Spirit of God." A matter this more terrible and startling, as he also says in the Epistle to the Thessalonians; for there too he uses an expression of this sort. "He that rejecteth, rejecteth not man, but God." So also here. If thou utter a reproachful word, if thou strike thy brother, thou art not striking him, thou art "grieving the Holy Spirit." And then is added further the benefit bestowed, in order to heighten the rebuke.

"Therefore he that rejecteth, rejecteth not man, but God, who giveth His Holy Spirit unto you." So that even if thou shouldest defile the Empress, he says, or even thine own handmaid, that hath a husband, the crime is the same. Why? Because He avenges not the persons that are injured, but Himself. For thou art equally defiled, thou hast equally insulted God; for both the one and the other is adultery, as both the one and the other is marriage. And though thou shouldest not commit adultery, but fornication, though the harlot has no husband, yet nevertheless God avenges, for He avenges Himself. For thou dost this act, not despising the man, so much as God. And it is manifest from this, that thou doest it concealing it from man, but thou pretendest that God doth not see thee. For tell me, if one who was thought worthy of the purple, and of infinite honor from the king (Emperor), and was commanded to live suitably to the honor, should go and defile himself with any woman; whom has he insulted? her, or the king who gave him all? She indeed is insulted too, but not equally.