The Messenger of Allah ﷺ said, "When one of you wakes up, he should not put his hand into his vessel," or he said, "into his water for ablution, until he has washed it three times, for he does not know where his hand spent the night."
حدثنا عبد الرزاق حدثنا معمر عن الزهري عن ابن المسيب أن
قال رسول الله ﷺ إذا استيقظ أحدكم فلا يدخل يده في إنائه أو قال في وضوئه حتى يغسلها ثلاث مرات فإنه لا يدري أين باتت يده
Its chain of transmission is sahih. It is a repetition of 7508, and we have already cited it at 7280, from this same route. Muslim also narrated it, 1:92, through Abdul-Razzaq, but did not mention its wording there.Al-Wadu, with fatha on the waw, means the water with which one performs wudu.