The narration states, "When one of you wakes from sleep, he should not dip his hand into his vessel until he has washed it three times, for he does not know where his hand spent the night."
حدثنا سفيان عن الزهري عن أبي سلمة
رواية إذا استيقظ أحدكم من نومه فلا يغمس يده في إنائه حتى يغسلها ثلاثا فإنه لا يدري أين باتت يده
Its isnad is sahih. His saying "as a report" means that it is attributed to the Prophet ﷺ. Muslim narrated it, 1:29, by way of Sufyan from Zuhri from Abu Salama, and by way of Maamar from Zuhri from Ibn Musayab, both of them from Abu Hurairah. He also narrated it before this with other chains. Malik narrated it in Muwatta, 21, from Abu Zinad from Araj from Abu Hurairah. Bukhari narrated it, 1:229–231, as part of a hadith, by way of Malik from Abu Zinad, and the rest of the group narrated it, as noted in al-Muntaqa, 229.