Musannaf Ibn Abi Shayba 1:2043

Abu Bakr narrated to us, he said: Husayn bin Ali narrated to us, from Abu Musa, who said: I passed by with Ibn Sirin on a path, and water dripped onto him from a rain gutter. He asked about it, and it was said to him that it was clean. He did not pay attention to it and did not care.