Kathir bin Abdullah bin Amr bin Awf al-Muzani narrates through his father and grandfather from Sayyiduna Bilal bin al-Harith (may Allah be pleased with him); he said: "When the Prophet (peace and blessings be upon him) went to relieve himself, he would go far away."
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1136