Bulugh al-Maram 38
Narrated Abu Huraira (rad):
Allah’s Messenger (ﷺ) said: “When one of you wakes up from his sleep, he must not put his hand in a utensil till he washed it three times, for he does not know where his hand was (while he slept)”.
[Agreed upon. This is Muslim’s version].
وَعَنْهُ: { إِذَا اِسْتَيْقَظَ أَحَدُكُمْ مِنْ نَوْمِهِ فَلَا يَغْمِسُ يَدَهُ فِي اَلْإِنَاءِ حَتَّى يَغْسِلَهَا ثَلَاثًا فَإِنَّهُ لَا يَدْرِي أَيْنَ بَاتَتْ يَدَهُ }  مُتَّفَقٌ عَلَيْهِ.‏ وَهَذَا لَفْظُ مُسْلِم ٍ  1‏ .‏‏1 ‏- صحيح.‏ رواه البخاري (162)‏، ومسلم (278)‏.‏