For washing all impurities, if they are on the ground, one washing that removes the substance of the impurity suffices. For anything other than the ground, seven washings are required, one of them with soil, in the case of impurity from a dog or a pig, …

His statement, “For washing all impurities, if they are on the ground, one washing that removes the substance of the impurity suffices”: this is a concession based on the location. Thus, if impurity falls upon the ground, its purification requires that the very substance of the impurity—whatever it may be—be removed by a single washing. If it cannot be removed except by two washings, then two are required; and if by three, then three.

The evidence for this is the Prophet’s saying, when the Bedouin urinated in the mosque: “Pour a bucket of water over his urine.” (1) He did not prescribe a particular number.

If the impurity has a tangible mass, it must first be removed, as when it is excrement or dried blood; it is then followed by washing with water.

If it is removed together with all the surrounding moisture—as, for example, if it is uprooted completely—then washing is not needed, because that which had been contaminated by the impurity has been removed.

His statement, “For anything other than the ground, seven washings are required,” means that washing impurities found on something other than the ground requires seven washings. Seven are necessary, with each washing distinct from the other: it is washed once and then wrung out, then washed a second time and wrung out, and so on until seven.

His statement, “one of them with soil, in the case of impurity from a dog or a pig,” means that one of the seven washings must be with soil.