Pray then like this: Our Father in heaven, hallowed be your name. (Mt 6:9)
This is, indeed, somewhat obscure, and not expressed in good German, for in our mother-tongue we would say: Heavenly Father, help that by all means Your name may be holy. But what is it to pray that His name may be holy? Is it not holy already? Answer: Yes, it is always holy in its nature, but in our use it is not holy. For God’s name was given us when we became Christians and were baptized, so that we are called children of God and have the Sacraments, by which He so incorporates us in Himself that everything which is God’s must serve for our use.
Here now the great need exists for which we ought to be most concerned, that this name have its proper honor, be esteemed holy and sublime as the greatest treasure and sanctuary that we have; and that as godly children we pray that the name of God, which is already holy in heaven, may also be and remain holy with us upon earth and in all the world.
But how does it become holy among us? Answer, as plainly as it can be said: When both our doctrine and life are godly and Christian. For since in this prayer we call God our Father, it is our duty always to deport and demean ourselves as godly children, that He may not receive shame, but honor and praise from us.
Martin Luther, Large Catechism III.36–39