It is narrated from Sayyiduna Zayd bin Harithah (may Allah be pleased with him) that Jibril (peace be upon him) came down to the Prophet (peace and blessings be upon him) at the time of the first revelation and taught him (peace and blessings be upon him) ablution and prayer. When he had finished, the Prophet (peace and blessings be upon him) took some water in his hand and sprinkled it on his private parts.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4641