Oaths and Vows (Kitab Al-Aiman Wa Al-Nudhur)
Dawud :: Book 21 : Hadith 3315
Narrated Ka'b ibn Malik:
I said: Apostle of Allah, to make my atonement complete I should divest myself of my all property as sadaqah (alms) for Allah and His apostle. He said: No. I said: The half of it. He said: No. I said: Then a third of it. He said: Yes. I said: I shall retain the portion I have at Khaybar.