Sahih Muslim Book 012, Hadith Number 3965.
Chapter : Disapproval of giving preference to tome children while making donation.
Nu'man b. Bashir reported: My father donated to me some of his property. My mother Amra bint Rawaha said: I shall not be pleased (with this act) until you make Allah's Messenger (may peace be upon him) a witness to it. My father went to Allah's Apostle (may peace be upon him) in order to make him the witness of the donation given to me. Allah's Messenger (may peace be upon him) said to him: Have you done the same with every son of yours? He said: No. Thereupon he (the Holy Prophet) said: Fear Allah, and observe equity in case of your children. My father returned and got back the gift.