The Messenger of Allah ﷺ said, "When one of you rises 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."
أخبرنا عمران بن يزيد قال حدثنا إسمعيل بن عبد الله قال حدثنا الأوزاعي قال حدثنا محمد بن مسلم الزهري قال حدثني سعيد بن المسيب قال حدثني
قال رسول الله ﷺ إذا قام أحدكم من الليل فلا يدخل يده في الإناء حتى يفرغ عليها مرتين أو ثلاثا فإن أحدكم لا يدري أين باتت يده
[Its chain is sahih] Tirmidhi transmitted it in the Book of Purification, chapter on what has been said about when one of you wakes up from sleep, etc., hadith 24, and Ibn Majah in the Book of Purification, chapter on the man who wakes up from his sleep, etc., hadith 393, from the hadith of Uzai, through the same chain, and Tirmidhi said, hasan sahih. Muslim also transmitted it, hadith 278, from the hadith of Zuhri, through the same chain.