I asked, "Messenger of Allah, tell me about ablution."He said, "Perform the ablution thoroughly, work water between the fingers, and inhale water deeply into the nose, unless you are fasting."
قلت: يا رسول الله، أخبرني عن الوضوء؟ قال: أسبغ الوضوء وخلل الأصابع، وبالغ في الاستنشاق إلا أن تكون صائما.
Abu Dawud (2366), Tirmidhi (788), Nasai (87), and Ibn Majah (407) all narrated it from the hadith of Yahya bin Salim, who said, Ismail bin Kathir related to me, saying, I heard Asim bin Laqit bin Sabra narrate from his father, and he mentioned it, sometimes at length and sometimes in brief.Tirmidhi said, "Hasan sahih." Ibn Khuzayma (150) and Ibn Hibban (1054) graded it sahih, as did Nawawi in al-Majmu and others. Its sourcing was mentioned earlier in the book on wudu.