Musnad Abu Ya'la al-Mawsili 3:50

Ubayd Allah narrated to us, Muhammad ibn Abd Allah ibn al-Zubayr narrated to us, Sufyan narrated to us, from Musa ibn Abi A’ishah, from Abd Allah ibn Zurayr, who said: Ali said to al-Abbas, "Ask the Prophet, may Allah bless him and grant him peace, to give you the treasury (al-khizanah)." So al-Abbas asked him, and the Prophet, may Allah bless him and grant him peace, said to him, "I will give you that which is better for you than that; it does not diminish you, nor do you diminish it." So he gave them the right to provide water (al-siqayah).