Maliks Muwatta Book 37, Hadith Number 2.
Section : Permissibility of the Bequest of the Child, the Simpleton, the Lunatic and the Idiot.
Malik related to me from Abdullah ibn Abi Bakr ibn Hazm that Amr ibn Sulaym az-Zuraqi informed his father that it had been said to Umar ibn al-Khattab, “There is here an adolescent boy who has not yet reached puberty. He is from the Ghassan tribe and his heir is in ash-Sham. He has property. Here he only has the daughter of one of his paternal uncles.” Umar ibn al-Khattab instructed, “Let him leave her a bequest.” He willed her a property called the well of Jusham.
Malik added, “That property was sold for 30,000 dirhams, and the daughter of the paternal uncle to whom he willed it was the mother of Amr ibn Sulaym az-Zuraqi.”