The Messenger of Allah ﷺ said, "When one of you wakes from sleep at night, he should not dip his hand into the water vessel until he has poured water over it two or three times, for none of you knows where his hand has spent the night."
حدثنا عبد الرحمن بن إبراهيم الدمشقي حدثنا الوليد بن مسلم حدثنا الأوزاعي حدثني الزهري عن سعيد بن المسيب وأبي سلمة بن عبد الرحمن أنهما حدثاه أن
قال رسول الله ﷺ إذا استيقظ أحدكم من الليل فلا يدخل يده في الإناء حتى يفرغ عليها مرتين أو ثلاثا فإن أحدكم لا يدري فيم باتت يده
[Sahih] Reported by Tirmidhi, Book of Purification, Chapter of what has been said about when one of you wakes from sleep... etc., no. 24, from the hadith of Walid through him, and he said, This hadith is hasan sahih, and its basis is found in Muslim, no. 278, and others.