盗ぬす人びとの上うわ前まえを取とる

expression

taking a cut from a thief's plunder; vile deed

Idiomatic expression describing a despicable act of stealing from a thief or profiting from ill-gotten gains. Often used figuratively to condemn morally corrupt behavior.

• 盗ぬす人びとの上うわ前まえを取とるような真似まねは、決けっしてしてはいけない。

  You must never do something as vile as taking a cut from a thief's plunder.