Matthew 6:9

After this manner therefore pray ye] Our Lord is not giving simply an illustration of the manner in which Christians ought to pray, but a set form of words to be learnt by heart and habitually used. This is clear from Luke 11:1, 'Lord, teach us to pray, as John also taught his disciples.' Every Jew was required to recite daily eighteen set prayers of considerable length, or, if hindered by press of business, a summary of them. The rabbis also taught their pupils an additional form of prayer composed by themselves, to be added to these eighteen prayers. Our Lord's disciples would therefore understand that they were to recite the Lord's Prayer every day at the end of their ordinary prayers. That this was done there can be little doubt, for 'The Teaching of the Twelve Apostles,' which probably dates from the 1st cent. a.d., directs the Lord's Prayer to be said three times a day by all Christians.

Our Lord's followers would further regard the prayer as a badge of discipleship, something intended to distinguish the disciples of Jesus from all other men. For this reason among others it has always been regarded as the prayer of the Church, not of the world. So jealously was its secrecy guarded in early times, that, like the Creed, it was only taught to catechumens just before their baptism, and was never used in those portions of public worship to which the heathen were admitted. It was always used at Holy Communion, where it formed the conclusion of the canon or prayer of consecration.
The Doxology ('for thine is the kingdom,' etc.), which is based on Jewish models, is no original part of the prayer. It was added as early as the 1st cent, in the Public Liturgy, and thence passed into the text of St. Matthew's Gospel, where it is found in many MSS.
The prayer is given by St. Luke (Luke 11:2) in a shorter form (the petitions 'thy will be done' and 'deliver us from evil' being omitted, see RV) and in a different historical connexion. Many account for this by supposing that the prayer was given twice, once complete and once abridged, but it is more probable that it was given only once, viz. on the occasion mentioned by St. Luke, and that St. Matthew has purposely placed it earlier, inserting it in our Lord's first recorded sermon in order to set before the reader at once a comprehensive view of His teaching about prayer. As to the form of the prayer, St. Matthew's version is, without doubt, to be preferred. It is not only fuller, but contains distinct marks of greater closeness to the original Aramaic.

The originality of the Lord's Prayer has sometimes been called in question, but without reason. The parallels adduced from rabbinical prayers are for the most part superficial, and prove no more than that our Lord availed Himself of current Jewish forms of expression.
The Lord's Prayer is generally divided into seven petitions, by some, however, into only six, the last two being reckoned as one. It falls into two distinct portions. The first portion, i.e. the first three petitions, is concerned chiefly with the glory of God; the second portion, i.e. the four latter petitions, with our own needs. Even those needs are mainly of a spiritual character. Bodily wants are mentioned in only one petition, and even that has been generally interpreted of spiritual as well as bodily needs.

Our Fatherwhich artinheaven] Christians are taught to say 'Our Father' not 'My Father' because they are brethren, and may not selfishly pray for themselves without praying for others. Every time they use this prayer they are reminded that they are a brotherhood, a society, a Holy Church, a family, of which the members are mutually responsible for one another's welfare, and cannot say, as Cain, 'Am I my brother's keeper?' This was also, though in a lower way, a principle of Judaism. The rabbis said, 'He that prays ought always, when he prays, to join with the Church' (i.e. to say 'we' instead of 'I'). God is never addressed as Father in the OT., and references to His Fatherhood are rare. Where they occur (Deuteronomy 32:6; Isaiah 63:16, etc.) He is spoken of as the Father of the nation, not of individual men. In the Apocrypha individuals begin to speak of God as their Father (Wis 2:16; Wis 14:3; Sir 23:1, Sir 23:4; Sir 51:10), and 'Our Father' becomes a fairly common form of address in later rabbinical prayers. Jesus first made the fatherhood of God the basis of religion, and gave it its full meaning. Since the Lord's Prayer is a distinctively Christian prayer, the prayer of the Church, not of humanity, 'Our Father' must be understood in its full Christian sense. In a certain sense God is the Father of all men. He is their Father because He created them, and because, in spite of sin, they are spiritually like Him, being made in His image. But He is the Father of Christians in an altogether new sense. They are His sons by adoption, reconciled to Him by the death of Christ; and, as a continual testimony that they are sons, He sends forth the Spirit of His Son into their hearts, crying, 'Abba,' i.e. 'Father.' Hence none but a Christian, i.e. one who by baptism 'has put on Christ,' and become 'a member of Christ, the child of God and an inheritor of the kingdom of heaven,' can rightly use the Lord's Prayer.

Which art in heaven] lit. 'in the heavens.' We are reminded that He who is called Father on earth, is also called Father in the heavens, by the hosts of angels who worship before His throne, and by the spirits of just men made perfect. Heaven is generally plural in NT. (as always in OT.) to indicate that there are various states of glory and blessedness assigned to different persons or to different celestial natures. The expression 'Our Father which art in heaven' is found in Jewish prayers.

Hallowed be thy name] i.e. let Thy Name be regarded as holy by all creatures both in heaven and earth. God's name is His revealed nature, i.e. practically God Himself. Observe that the glory of God, not human needs, is here put first. 'Hallowed be Thy Name' is a prayer that God may be rightly worshipped, and its utterance is in itself an act of worship.

The prayer begins with worship, because worship is the highest spiritual activity of man. It is higher than petition. An unspiritual man can ask for benefits, but no one can worship who does not in his inmost soul apprehend what God is. To worship is to give God His due, to be penetrated with a sense of His perfections, His infinity, His majesty, His holiness, His love, and to prostrate body and soul before Him. In the worship of God is included also due reverence towards all that is God's, or comes from God. We 'hallow His Name, 'when we reverence His holy Word, His day, His Sacraments, His Church, His ministers, His saints, and the revelation which He makes to us outwardly through nature, and inwardly in our own souls through the voice of reason and conscience.