Sayyidah Zaynab bint Jahsh (may Allah be pleased with her) narrates: The Prophet (peace and blessings be upon him) was sleeping at her house, and Husayn was crawling about the house. Sayyidah Zaynab's (may Allah be pleased with her) attention drifted from him, and he crawled until he came to the Prophet (peace and blessings be upon him) and climbed onto his stomach. Then he placed his private part on the navel of the Prophet (peace and blessings be upon him) and urinated. Sayyidah Zaynab (may Allah be pleased with her) narrates: The Prophet (peace and blessings be upon him) woke up. I got up, went towards Husayn and wanted to move him away from the Prophet (peace and blessings be upon him), but the Prophet (peace and blessings be upon him) said: Leave my son! When he had finished urinating, the Prophet (peace and blessings be upon him) took a vessel of water and poured it over it, and said: Water is poured over the urine of a boy, and the urine of a girl is washed. After this the narrator recorded the full hadith.
Imam al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains a narrator, Layth bin Abi Sulaym, in whom there is weakness.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1572