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 Thy 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.
Now the name of God is profaned by us either in words or in works. (For whatever we do upon the earth must be either words or works, speech or act.) In the first place, then, it is profaned when men preach, teach, and speak in the name of God what is false and misleading, so that His name must serve to adorn and to find a market for falsehood. That is, indeed, the greatest profanation and dishonor of the divine name. Furthermore, also when men, by swearing, cursing, conjuring, etc., grossly abuse the holy name as a cloak for their shame. In the second place also by an openly wicked life and works, when those who are called Christians and the people of God are adulterers, drunkards, misers, envious, and slanderers. Here again must the name of God come to shame and be profaned because of us. For just as it is a shame and disgrace to a natural father to have a bad perverse child that opposes him in words and deeds, so that on its account he suffers contempt and reproach, so also it brings dishonor upon God if we who are called by His name and have all manner of goods from Him teach, speak, and live in any other manner except as godly and heavenly children, so that people say of us that we must be not God's, but the devil's children.
Thus you see that in this petition we pray just for that which God demands in the Second Commandment; namely, that His name be not taken in vain to swear, curse, lie, deceive, etc., but be usefully employed to the praise and honor of God. For whoever employs the name of God for any sort of wrong profanes and desecrates this holy name, as aforetime a church was considered desecrated when a murder or any other crime had been committed in it, or when a pyx or relic was desecrated, as being holy in themselves, yet become unholy in use. Thus this point is easy and clear if only the language is understood, that to hallow is the same as in our idiom to praise, magnify, and honor both in word and deed.
Here, now, learn how great need there is of such prayer. For because we see how full the world is of sects and false teachers, who all wear the holy name as a cover and sham for their doctrines of devils, we ought by all means to pray without ceasing, and to cry and call upon God against all such as preach and believe falsely and whatever opposes and persecutes our Gospel and pure doctrine, and would suppress it, as bishops, tyrants, enthusiasts, etc. Likewise also for ourselves who have the Word of God, but are not thankful for it, nor live as we ought according to the same. If now you pray for this with your heart, you can be sure that it pleases God; for He will not hear anything more dear to Him than that His honor and praise is exalted above everything else, and His Word is taught in its purity and is esteemed precious and dear.