Abu Dawud Book 18, Hadith Number 3630.

Narated By Abdullah ibn az-Zubayr : A man disputed with az-Zubayr about streamlets in the lava plain which was irrigated by them. The Ansari said: Release the water and let it run, but az-Zubayr refused. The Holy Prophet (PBUH) said to az-Zubayr: Water (your ground), Zubayr, then let the water run to your neighbour. The Ansari then became angry and said: Apostle of Allah! it is because he is your cousin! Thereupon the face of the Apostle of Allah (PBUH) changed colour and he said: Water (your ground), then keep back the water till it returns to the embankment. Az-Zubayr said: By Allah! I think this verse came down about that: “But no, by thy Lord! they can have no (real) faith, until they make thee judge…”