Sahih Bukhari Volume 003, Book 040, Hadith Number 549.
Narated By 'Urwa : When a man from the Ansar quarrelled with AzZubair, the Prophet said, "O Zubair! Irrigate (your land) first and then let the water flow (to the land of the others)." "On that the Ansari said, (to the Prophet), "It is because he is your aunt's son." On that the Prophet said, "O Zubair! Irrigate till the water reaches the walls between the pits around the trees and then stop (i.e. let the water go to the other's land)." I think the following verse was revealed concerning this event: "But no, by your Lord They can have No faith Until they make you judge In all disputes between them." (4.65)