Intriguing information about the German lyrics not being from Claudius. I'll look a bit more. The online information I usually trust most is the German Volkslederarchiv (folk song archive).

It has Matthias Clausius as the author:

Schlafe schlafe holder süßer Knabe (a four verses German version)

A near repetition of verse 3 is given there as verse 4:

Schlafe, schlafe in der Mutter Schoße,
Noch umtönt dich holder Liebeston,
Eine Lilie, eine Rose
Nach dem Schlafe wird sie dir zum Lohn.

I think this is the first time I have ever encountered the word "Labe" as a noun. Even as a verb it is now close to unknown in the young generation.

Wolfgang