On the Lord's Prayer 31

And when we stand for prayer, dearest brothers, we ought to be watchful and apply ourselves to our petitions with our whole heart. Let every fleshly and worldly thought depart, and let the mind think of nothing but that alone for which it prays. For this reason the priest too, before the prayer, prepares the minds of the brothers by first saying a preface: "Lift up your hearts," so that, when the people answer, "We lift them up to the Lord," they may be reminded that they ought to think of nothing but the Lord. Let the heart be closed against the adversary and be open to God alone, and let it not allow the enemy of God to approach it at the time of prayer. For he often creeps in and penetrates, and, subtly deceiving, calls our prayers away from God, so that we have one thing in our heart and another in our voice, when not the sound of the voice but the mind and heart ought to pray to the Lord with sincere intention. And what sloth it is to be distracted and carried away by foolish and profane thoughts when you are praying to the Lord, as if there were anything you ought to think of more than that you are speaking with God! How do you ask to be heard by God when you do not hear yourself? Do you want the Lord to be mindful of you when you pray, when you yourself are not mindful of yourself? This is to be altogether off guard against the enemy; this is, when you pray to God, to offend the majesty of God by carelessness in prayer; this is to be awake with the eyes and asleep in the heart, whereas a Christian ought, even when asleep in the eyes, to be awake in the heart, as it is written in the person of the church speaking in the Song of Songs: "I sleep, and my heart is awake." Therefore the apostle warns anxiously and carefully, saying: "Persevere in prayer, watching in it"; teaching, of course, and showing that those can obtain what they ask of God whom God sees watchful in prayer.