Abu Dawud Book 15, Hadith Number 3311.

Narated By Ka’b ibn Malik : I said: Apostle of Allah, to make my repentance complete I should divest myself of my property as sadaqah (alms) for Allah and His Apostle. The Apostle of Allah (PBUH) said: Retain some of your property, for that will be better for you. So he said: I shall retain the portion I have at Khaybar.