In most religions, when the Lord's Prayer is recited, the phrase "For Thine is the kingdom, and the power, and the glory forever. Amen" is deleted. That same phrase is not included in the Matthew and Luke versions of the same prayer. The reason for adding such a phrase is quit obvious to me. When was this phrase added to the Lord's Prayer? Who added it?
The phrase "For Thine is the kingdom, and the power, and the glory forever. Amen" dates back to some very early manuscripts of Matthew’s gospel. It is omitted in some early manuscripts. There is no reason to believe that those that did include it were not accurate copies of Matthew’s gospel. Instead, those that omit it may have been trying to match it exactly to Luke’s account. There is nothing to indicate that Jesus did not add this phrase originally.
It is true that Luke does not include that phrase in his version of the prayer. However, this is not the only instance in which one or the other of the gospel writers left out something that was included by another. To get this fuller view of what was said and done may be one reason we have four gospel accounts. Because Luke does not include this phrase does not mean that Matthew was wrong. It just means that Luke chose not to include it.
Please see my article at The Lord's Prayer, Part 3 for more of my analysis on this part of what is sometimes called the Lord’s Prayer.