Muwatta Malik 37
موطأ مالك#37SahihYahya related to me from Malik from Abu'zZinad from al-Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, "When you wake up from sleep to pray, wash your hands before you put them in the wudu water, for you do not know where your hands have spent the night
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Salim al-HilaliSahih
In-book reference: 2:6