Anyone who prays should pray having his heart in touch with his mouth and his mind with his lips. If, however, he bows down and stretches out his hands in prayer while his heart is daydreaming somewhere else, then he is like the cedars which storms bend down and flatten out. Or if his lips are eagerly murmuring but his mind is somewhere [else], then this resembles the case of doors being buffeted by the winds, which no one can open or shut.
For anyone who stands in prayer a discerning compassion is required. Tears of compunction are also beneficial. He also requires a recollected mind. If he has any grudge against any of his fellows, he should wash this away from his heart. And he should pray in silence, his lips murmuring with awareness. And when he puts the seal on his prayer, let him stop and remain still in silence. He should not occupy himself with empty talk or with unedifying chatter; rather, he should remain in silence and awareness. Then his prayer will be fully accepted by him who receives prayers and pure thoughts.
Philoxenus of Mabbug (obit. 523 AD)