I'm fairly regularly in a situation where a group of people prays the Lord's Prayer together. (For example, our weekly community men's Bible study closes each meeting that way.) No matter the setting, we recite the Lord's Prayer this way:
Our Father, who art in heaven, hallowed by thy name. Thy kingdom come. Thy will be done on earth as it is in heaven. Give us this day our daily bread. Forgive us our debts as we forgive our debtors. Lead us not into temptation but deliver us from evil. For thine is the kingdom and the power and the glory forever. Amen.
(Often there's one or two people who use "trespasses" instead of "debts," and some people say "forever and ever" instead of "forever," but what I've printed above is the most common form.)
We say the Lord's Prayer that way because that's the way we learned it. Elderly nursing home residents learned the Lord's Prayer that way when they were children. I learned it that way when I was a child. It's easy and good to use the prayer the way we first learned it.
But here's the thing: I have never owned a Bible that translates the Lord's Prayer that way. The form of the Lord's Prayer I've printed above is a cross between the King James Version and the Revised Standard Version. I've never regularly attended a church that still used either of those Bible translations in worship. I don't use "thee" and "thou" and "thy" when I speak or write, nor do I know anyone (as far as I know) who uses that language in everyday communication.
So why do we still say the Lord's Prayer that way? The answer, of course, is because we learned it that way. But why do we still teach it that way? Again, probably because we learned it that way. But I think that's a mostly silly reason. Using "thee" and "thou" and "thy" in prayer isn't wrong. The extra formality can remind us of God's greatness and help us be respectful. But we don't need to be extra formal in prayer. The words Jesus used when He taught His disciples this prayer were not extra formal, so we don't need to translate them that way. I think that teaching children this prayer with language they don't normally use and might not understand increases the risk that they will simply recite this prayer without much thought or meaning. And that's what we should really try to avoid when we use the Lord's Prayer.
If we pray the Lord's Prayer on our own, I think we should pray it however seems most comfortable and natural to us. If we use it with a group who all learned to use "thy," we should feel free to continue to do so. But if we pray the Lord's Prayer with those who are still learning it, such as in a normal church service, I really think we should use more contemporary and accessible language. It may be a bit uncomfortable for some of us who've done this before, but I think it'll help at least the newest of us (and maybe all of us) understand a little better. I'll even leave you the text from the NIV, which is pretty close to how I learned it but much closer to how I speak and think and understand:
Our Father in heaven, hallowed be your name, your kingdom come, your will be done, on earth as it is in heaven. Give us today our daily bread. And forgive us our debts, as we also have forgiven our debtors. And lead us not into temptation, but deliver us from the evil one. For yours is the kingdom and the glory and the power forever. Amen.
Grace and peace,
BMH
P.S. We maybe shouldn't use "hallowed" anymore either. We could use something like "make your name holy" or "may your holy name be honored." However, the NIV is meant to be written at an average reading level, and it keeps "hallowed." I'll keep thinking it about that.