Answer: When a person makes sure that he does not wrong his neighbor in any way whatsover, then let him be sure that his prayer is acceptable to God (see Ex 20:16-7; Mt 19:19). But if someone harms his neighbor in any way whatsoever, either physically or spiritually, his prayer is an abomination and is unacceptable. For the wailing of the one who is being wronged will never allow this person’s prayer to come before the face of God. And if indeed he does not quickly reconcile with his neighbor, he will certainly not go unpunished his whole life by his own sins, for it is written that whatever you bind on earth will be bound in heaven (Mt 18:18).
Tim Vivian, ed., Becoming Fire: Through the Year with the Desert Fathers and Mothers. (Collegeville: Cistercian Studies, 2008).