Musnad Abu Ya'la al-Mawsili 42:303

Zuhayr narrated to us, Rab'i ibn Ibrahim narrated to us, Abd al-Rahman ibn Ishaq narrated to us, from Abd al-Rahman ibn Mu'awiyah, from al-Harith, the freed slave of Ibn Siba', from Abu Sa'id, that the Prophet (peace and blessings of Allah be upon him) said: "Whoever seeks sufficiency, Allah will make him sufficient, and whoever seeks chastity, Allah will make him chaste."