It is narrated from Sayyiduna Nu'man bin Bashir (may Allah be pleased with them both): My father gave me a gift. Isma'il bin Salim, among the narrators, said: He gave him a slave. Nu'man (may Allah be pleased with him) said: My mother, Amrah bint Rawahah (may Allah be pleased with her), said: Go to the Messenger of Allah (peace and blessings be upon him) and make him a witness. So he came to the Prophet (peace and blessings be upon him) and mentioned it to him, saying: I have given my son Nu'man a gift, and Amrah has asked me to make you a witness to it. He (peace and blessings be upon him) asked: "Do you have other children besides him?" He said: Yes. He (peace and blessings be upon him) said: "Have you given all of them the same as Nu'man?" He said: No. Some of the hadith narrators reported that he (peace and blessings be upon him) said: "This is injustice." And some said: It is a gift singled out for him to the exclusion of the others, or a sham gift under pressure. He (peace and blessings be upon him) said: "Then make someone other than me a witness." In the wording of Mughirah: "Would it not please you that they be equal towards you in kindness and gentleness?" He said: Yes. He (peace and blessings be upon him) said: "Make someone other than me a witness." And Mujalid mentioned in his narration: "They have a right over you that you be just between them, just as you have a right over them that they treat you with kindness."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الهبات / 12002