The first two verses of the hymn Away in a Manger were said to be written by Martin Luther and originally called Luther's Cradle Song, written for his children. Originally, it didn't have a tune attached to it. When it was published in 1885 it was titled Away in a Manger and had a tune with it. The third stanza - my favorite - was written by Charles H. Gabriel and published in 1892. Wikipedia says Gabriel credited the entire text to Luther and gave it the title Cradle Song.
But it turns out some people think Luther didn't write it because there is no record of it in his papers. Some say it was written 400 years after Luther's birth and attributed to him as a marketing ploy.
Honestly, I don't have a dog in this fight and don't much care who wrote it. I simply love those lyrics because they are a prayer: the quietest cry of the human heart.
Be with me, Lord Jesus! Stay close by me. Amen!