Musannaf Ibn Abi Shayba 5:972

Mu'tamir narrated to us, from Ma'mar al-Dabbi, who said: While a group of people were with me, asking or digging up the earth, they struck a treasure, and Muhammad ibn Jabir al-Rasibi was among them. He wrote about it to 'Adi, and 'Adi wrote to Umar ibn Abd al-Aziz. Umar wrote: "Take from it the fifth, and write for them a release."