Hadith.6 - Ali ibn Ja'far asked his brother, Imam Musa ibn Jafar Al-Kadhim (as) about a roof where people urinate and perform ritual washing after major impurity (ghusl), and then it rains. He asked: "Can the water that flows from it be used for ablution (wudu) for prayer?" Imam (as) said: "If it flows, there is no harm in it."