Babylonian Talmud, Bava Metzia 83a
תלמוד בבלי - מסכת בבא מציעא
We need [this statement] for the case in which the employer raises the workers’ wages. In the case in which he says to them, “I raised your wages in order that you would begin work early and stay late,” they may reply, “You raised our wages in order that we would do better work.”

