We are seeking in our prayers that God might be attentive to us, according to the text: Be attentive to me and hear me (Ps 55:3). Now how likely is it that he will do this, if we are not attentive to ourselves? It is from the heart that prayer takes most of its power. According to Saint Isidore: "Prayer is of the heart, not of the lips." For God does not attend merely to the words of the one beseeching him, but he looks rather on the heart of the man who prays. So the man who does not have his heart in his prayer takes away from prayer what is best in it. So it is clear from all this that the heart’s intention is necessary in prayer. So that this may be more easily done, the heart must be first recollected when one comes to pray.
BLESSED HUMBERT OF ROMANS, O.P.
