Musannaf Ibn Abi Shayba 1:1038

Abu Khalid al-Ahmar narrated to us, from Muhammad ibn ‘Ajlan, from Abu al-‘Awwam, who said: I was sitting with Ibn ‘Umar when a Bedouin came and said to him, "We stay away with the livestock from water, and one of us needs to be with his wife." He said, "As for Ibn ‘Umar, he would not do that. But as for you, when you find water, then perform ghusl."