Objection 1. It would seem that the seven petitions of the Lord's Prayer are not fittingly assigned. It is useless to ask for that to be hallowed which is always holy. But the name of God is always holy, according to Luke 1:49, "Holy is His name." Again, His kingdom is everlasting, according to Psalm 144:13, "Thy kingdom is a kingdom of all ages." Again, God's will is always fulfilled, according to Isaiah 46:10, "All My will shall be done." Therefore it is useless to ask for "the name of God to be hallowed," for "His kingdom to come," and for "His will to be done."
Objection 2. Further, one must withdraw from evil before attaining good. Therefore it seems unfitting for the petitions relating to the attainment of good to be set forth before those relating to the removal of evil.
Objection 3. Further, one asks for a thing that it may be given to one. Now the chief gift of God is the Holy Ghost, and those gifts that we receive through Him. Therefore the petitions seem to be unfittingly assigned, since they do not correspond to the gifts of the Holy Ghost.
Objection 4. Further, according to Luke, only five petitions are mentioned in the Lord's Prayer, as appears from the eleventh chapter. Therefore it was superfluous for Matthew to mention seven.
Objection 5. Further, it seems useless to seek to win the benevolence of one who forestalls us by his benevolence. Now God forestalls us by His benevolence, since "He first hath loved us" (1 John 4:19). Therefore it is useless to preface the petitions with the words our "Father Who art in heaven," which seem to indicate a desire to win God's benevolence.
On the contrary, The authority of Christ, who composed this prayer, suffices.
I answer that, The Lord's Prayer is most perfect, because, as Augustine says (ad Probam Ep. cxxx, 12), "if we pray rightly and fittingly, we can say nothing else but what is contained in this prayer of our Lord." For since prayer interprets our desires, as it were, before God, then alone is it right to ask for something in our prayers when it is right that we should desire it. Now in the Lord's Prayer not only do we ask for all that we may rightly desire, but also in the order wherein we ought to desire them, so that this prayer not only teaches us to ask, but also directs all our affections. Thus it is evident that the first thing to be the object of our desire is the end, and afterwards whatever is directed to the end. Now our end is God towards Whom our affections tend in two ways: first, by our willing the glory of God, secondly, by willing to enjoy His glory. The first belongs to the love whereby we love God in Himself, while the second belongs to the love whereby we love ourselves in God. Wherefore the first petition is expressed thus: "Hallowed be Thy name," and the second thus: "Thy kingdom come," by which we ask to come to the glory of His kingdom.
To this same end a thing directs us in two ways: in one way, by its very nature, in another way, accidentally. Of its very nature the good which is useful for an end directs us to that end. Now a thing is useful in two ways to that end which is beatitude: in one way, directly and principally, according to the merit whereby we merit beatitude by obeying God, and in this respect we ask: "Thy will be done on earth as it is in heaven"; in another way instrumentally, and as it were helping us to merit, and in this respect we say: "Give us this day our daily bread," whether we understand this of the sacramental Bread, the daily use of which is profitable to man, and in which all the other sacraments are contained, or of the bread of the body, so that it denotes all sufficiency of food, as Augustine says (ad Probam, Ep. cxxx, 11), since the Eucharist is the chief sacrament, and bread is the chief food: thus in the Gospel of Matthew we read, "supersubstantial," i.e. "principal," as Jerome expounds it.
We are directed to beatitude accidentally by the removal of obstacles. Now there are three obstacles to our attainment of beatitude. First, there is sin, which directly excludes a man from the kingdom, according to 1 Corinthians 6:9-10, "Neither fornicators, nor idolaters, etc., shall possess the kingdom of God"; and to this refer the words, "Forgive us our trespasses." Secondly, there is temptation which hinders us from keeping God's will, and to this we refer when we say: "And lead us not into temptation," whereby we do not ask not to be tempted, but not to be conquered by temptation, which is to be led into temptation. Thirdly, there is the present penal state which is a kind of obstacle to a sufficiency of life, and to this we refer in the words, "Deliver us from evil."
Reply to Objection 1. As Augustine says (De Serm. Dom. in Monte ii, 5), when we say, "Hallowed be Thy name, we do not mean that God's name is not holy, but we ask that men may treat it as a holy thing," and this pertains to the diffusion of God's glory among men. When we say, "Thy kingdom come, we do not imply that God is not reigning now," but "we excite in ourselves the desire for that kingdom, that it may come to us, and that we may reign therein," as Augustine says (ad Probam, Ep. cxxx, 11). The words, "Thy will be done rightly signify, 'May Thy commandments be obeyed' on earth as in heaven, i.e. by men as well as by angels" (De Serm. Dom. in Monte ii, 6). Hence these three petitions will be perfectly fulfilled in the life to come; while the other four, according to Augustine (Enchiridion cxv), belong to the needs of the present life.
Reply to Objection 2. Since prayer is the interpreter of desire, the order of the petitions corresponds with the order, not of execution, but of desire or intention, where the end precedes the things that are directed to the end, and attainment of good precedes removal of evil.
Reply to Objection 3. Augustine (De Serm. Dom. in Monte ii, 11) adapts the seven petitions to the gifts and beatitudes. He says: "If it is fear God whereby blessed are the poor in spirit, let us ask that God's name be hallowed among men with a chaste fear. If it is piety whereby blessed are the meek, let us ask that His kingdom may come, so that we become meek and no longer resist Him. If it is knowledge whereby blessed are they that mourn, let us pray that His will be done, for thus we shall mourn no more. If it is fortitude whereby blessed ere they that hunger, let us pray that our daily bread be given to us. If it is counsel whereby blessed are the merciful, let us forgive the trespasses of others that our own may be forgiven. If it is understanding whereby blessed are the pure in heart, let us pray lest we have a double heart by seeking after worldly things which ere the occasion of our temptations. If it is wisdom whereby blessed are the peacemakers for they shall be called the children of God, let us pray to be delivered from evil: for if we be delivered we shall by that very fact become the free children of God."
Reply to Objection 4. According to Augustine (Enchiridion cxvi), "Luke included not seven but five petitions in the Lord's Prayer, for by omitting it, he shows that the third petition is a kind of repetition of the two that precede, and thus helps us to understand it"; because, to wit, the will of God tends chiefly to this--that we come to the knowledge of His holiness and to reign together with Him. Again the last petition mentioned by Matthew, "Deliver us from evil," is omitted by Luke, so that each one may know himself to be delivered from evil if he be not led into temptation.
Reply to Objection 5. Prayer is offered up to God, not that we may bend Him, but that we may excite in ourselves the confidence to ask: which confidence is excited in us chiefly by the consideration of His charity in our regard, whereby he wills our good--wherefore we say: "Our Father"; and of His excellence, whereby He is able to fulfil it--wherefore we say: "Who art in heaven."
Source: Summa Theologica (New Advent)