Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: Once the Prophet (peace and blessings be upon him) was sleeping in one of his houses. Meanwhile Sayyiduna al-Hasan (may Allah be pleased with him) came and sat on the chest of the Prophet (peace and blessings be upon him), and he urinated on the chest of the Prophet (peace and blessings be upon him). I went to remove him, and the Prophet (peace and blessings be upon him) woke up. He said: O Anas! Woe to you! Leave my son and the fruit of my heart! For whoever harms him harms me, and whoever harms me harms Allah Almighty. Then the Prophet (peace and blessings be upon him) called for water and poured it over the urine. He (peace and blessings be upon him) said: Water is poured over the urine of a boy, and the urine of a girl is washed.
Imam al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains a narrator, Nafi' Abu Hurmuz, on whose being da'if (weak) the hadith scholars agree.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1570