I say, and with God's success: The leftover water of sheep is pure and purifying for ritual impurity, as it removes actual impurity from clothing and the body, and it removes ritual impurity, which is the state of being in need of ablution or major ritual purification. It is permissible to perform ablution and bathing with it because its saliva is derived from its flesh, and its flesh is pure. This is unless it is a jallalah - meaning it eats filth, which is originally dung. However, if it is a jallalah, its leftover water is disliked. The same ruling applies to the leftover water of every animal whose meat is permissible to eat, such as cows and camels. See: Al-Maraqi, p. 29, and God knows best.