Titus of Bostra — as excerpted in the Catena Aurea on Luke 11:1-4

“(in Matt.) The disciples having seen a new way of life, desire a new form of prayer, since there were several prayers to be found in the Old Testament. Hence it follows, When he ceased, one of his disciples said to him, Lord, teach us to pray, in order that we might not sin against God in asking for one thing instead of another, or by approaching God in prayer in a manner that we ought not.”