“Teach us to pray”
“We need words to help us recollect ourselves and see what we are asking for; not to make us suppose that the Lord must be given information or swayed by words. So when we say, “Hallowed be thy name,” we are counselling ourselves to desire that his name, which is always holy, may be held holy also among men; that is, that it may not be treated with contempt: and this for the benefit not of God but of men. When we say, “Thy kingdom come,” which will certainly come whether we wish it or not, we arouse our desire for that kingdom, that it may come for us, and that we may be worthy to reign therein. When we say, “Thy will be done on earth as it is in heaven,” we are asking him for obedience for ourselves, that his will may be done in us as it is done in heaven by his angels…
When we say, “Forgive us our trespasses as we forgive those who trespass against us,” we are advising ourselves both as to what we should ask for, and what we should do to be worthy to receive it… When we say, “Deliver us from evil,” we bring ourselves to reflect that we are not yet in that happy state where we shall suffer no evil. This last petition in the Lord’s prayer has such a wide scope that a Christian may in any trouble express his pain by it, pour forth his tears, begin from it, linger over it, and end his prayer at this point.
It is necessary by these words to impress the realities themselves on our memory. For whatever other words we may say… if we are praying in the right way, we say nothing that has not already a place in the Lord’s prayer.”
Saint Augustine (354-430), Letter 130, to Proba on prayer, 11-12 (trans. cf Breviary, Tuesday of the 29th week)