Ruling 219

The urine and faeces of an animal that habitually eats human excrement is impure. In order for the urine and faeces of such an animal to be considered pure, the animal must be put through a process of istibrāʾ,²⁵ meaning that it must be prevented from eating impurity for some time and be fed pure food so that after that period of time, it is no longer considered to be an excrement-eating animal. The recommended precaution is to prevent an excrement-eating camel from eating excrement for forty days, a cow twenty days, a sheep ten days, a duck seven or five days, and a domestic hen three days, even if before these time periods are over the animal in question ceases to be considered an excrement-eating animal.

²⁵ The meaning of istibrāʾ here is different to that mentioned in two other places in this work: firstly, in Ruling 69, where it refers to the process of clearing the male urethra of urine after urinating; and secondly, in Ruling 495, where it refers to the method of checking whether or not menstruation has stopped.