Cyril of Alexandria — as excerpted in the Catena Aurea on Luke 11:5-8

“The Saviour had before taught, in answer to the request of His apostles, how men ought to pray. But it might happen that those who had received this wholesome teaching, poured forth their prayers indeed according to the form given to them, but carelessly and languidly, and then when they were not heard in the first or second prayer, left off praying. That this then might not be our case, He shews by means of a parable, that cowardice in our prayers is hurtful, but it is of great advantage to have patience in them. Hence it is said, And he says unto them, Which of you shall have a friend.”