Yiddish: When you put a bird in a cage, you don't know whether it's laughing or crying.

SOURCE: Bernstein, Jüdische Sprichwörter und Redensarten.

‏‏אַז מען זעצט אַ פֿייגעלע אין שטײַגעלע אַרײַן, ווייס מען ניט צי לאַכט עס צי וויינט עס.

Az men zetst a feygele in shtaygele arayn, veys men nit tsi lakht es tsi veynt es.

When you put a bird in a cage, you don't know whether it's laughing or crying.