The Messenger of Allah ﷺ said, "When one of you wakes from sleep, he should not put his hand into the vessel until he has washed it."
قال رسول الله ﷺ: إذا استيقظ أحدكم من نومه فلا يدخل يده في الإناء حتى يغسلها.
Ibn Majah (394) and Ibn Khuzayma (146) both narrated it from the hadith of Abdullah bin Wahb, who said, Ibn Lahia and Jabir bin Ismail informed me, from Aqeel bin Khalid, from Ibn Shihab, from Salim bin Abdullah, from his father, who said, and then he mentioned it. The wording given is that of Ibn Majah, while the wording of Ibn Khuzayma is, "Let him not put his hand into the vessel until he washes it three times, for he does not know where his hand spent the night or where it wandered." A man said to him, "What do you think if it were a large pool?" Ibn Umar threw a pebble at him and said, "I tell you about the Messenger of Allah and you say, 'What do you think if it were a pool?'"Ibn Khuzayma said, "Ibn Lahia is not among those whose hadith I include in this book when he narrates alone, but I have included this report because Jabir bin Ismail is with him in the chain."I say, the one who narrated from Ibn Lahia here is Abdullah bin Wahb, the Egyptian, who was among those who heard from him early on, so his narration from him is sound even if he is not corroborated by another narrator.This hadith indicates that it is disliked to dip the hands into the vessel before washing them. As for one who puts them in before washing, according to the soundest of the scholars' opinions, the water does not become impure nor does it lose its purifying quality, but one should not be careless about such matters of prescribed etiquette, since observing them brings general benefit and cuts off doubts and misgivings.