Maliks Muwatta Book 2, Hadith Number 14.

Section : What is Pure for Wudu.

Yahya related to me from Malik from Yahya ibn Said from Muhammad ibn Ibrahim ibn alHarith at-Taymi from Yahya ibn Abd ar-Rahman ibn Hatib that Umar ibn al-Khattab set out on one occasion with a party of riders, one of whom was Amr ibn al-As. They came to a watering place and Amr ibn al-As asked the man who owned it whether wild beasts drank from it. Umar ibn al-Khattab told the owner of the watering place not to answer, since the people drank after the wild beasts and the wild beasts drank after them.