PRAYERS are those by which we offer or vow something to God, what the Greeks call evki, i.e., a vow……
We pray, when we renounce this world and promise that being dead to all worldly actions and the life of this world we will serve the Lord with full purpose of heart.
We pray when we promise that despising secular honors and scorning earthly riches we will cleave to the Lord in all sorrow of heart and humility of spirit.
We pray when we promise that we will ever maintain the most perfect purity of body and steadfast patience, or when we vow that we will utterly root out of our heart the roots of anger or of sorrow that worketh death.
John Cassian’s Conferences, The First Conference OF Abbot Isaac On Prayer, NPNP2.11