~ Drum prüfe wer sich ewig bindet ~
This is an excerpt from Das Lied von der Glocke (The Song of the Bell) written by Friedrich Schiller in 1799. This is a more literal translation and another suggests that the meaning is "Look before you leap and make sure your heart is in it". It would seem from the scene with a wife chastising her husband, that the translation given here is more to the point. The stein is post WWII.
Drum prüfe
wer sich ewig bindet,
ob sich auch Herz zum Herzen findet!
Therefore prove
to whom you are eternally bound,
whether your heart is really in it!
Translation: Roy De Selms
Photo credit: Unknown