The Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, narrated to me from Ahmad ibn Muhammad, from his father, from Al-Husayn ibn Al-Hasan ibn Aban, from Al-Husayn ibn Sa'id, from Al-Nadr ibn Suwayd, from Abdullah ibn Sinan, from Abu Abdullah عليه السلام. Imam عليه السلام said: "If a small animal falls into the well or a person in a state of major ritual impurity (junub) descends into it, seven buckets must be drawn from it. But if a bull or something similar dies in it, or wine is poured into it, then all the water must be drawn out."