Sayyiduna al-Asla' (may Allah be pleased with him) said: I used to serve the Prophet (peace and blessings be upon him) and saddle his mount for him. One night he (peace and blessings be upon him) said to me: "O Asla', get up and saddle the mount." I said: O Messenger of Allah, I am in a state of major ritual impurity (janabah). He said: The Messenger of Allah (peace and blessings be upon him) fell silent, then Jibril (peace be upon him) came with the verse of tayammum, and the Messenger of Allah (peace and blessings be upon him) said: "O Asla', get up and perform tayammum." I got up and performed tayammum, then saddled the mount for him (peace and blessings be upon him). He (peace and blessings be upon him) travelled on until he passed by some water, and he said to me: "O Asla', let this water touch your body." He said: And my father showed me tayammum just as his father had shown him: one strike for the face, and one strike for the two hands up to the elbows.
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 871