Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) had himself cupped and gave the cupper his wage, and had it been impure (earnings), he (peace and blessings be upon him) would not have given it to him to eat.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11819