It was narrated from Salim from his father that:
The Messenger of Allah said: "When anyone of you wakes up from sleep, he should not put his hand into the vessel until he has washed it." (TH)
English reference (TH): Vol. 1, Book 1, Hadith 394 (TH)
Arabic reference (TH): Book 1, Hadith 426 (TH)