Musnad Abu Ya'la al-Mawsili 83:2

'Abd al-A'la narrated to us, Hammad narrated to us, from 'Ali ibn Zayd, from Abu Hurrah al-Raqashi, from his uncle, that the Prophet (peace and blessings of Allah be upon him) said: "The wealth of a Muslim man is not lawful except by his own good pleasure."