so it takes the genitive case by adjacency. An example is the Arabs’ saying: “This is the ruined burrow of a lizard,” with “ruined” in the genitive case, even though it is an adjective describing “burrow,” which is nominative. According to grammatical rules, “ruined” should be nominative, since the adjective of a nominative noun is nominative; but the Arabs placed it in the genitive by adjacency. (1)

The second explanation is that the accusative reading indicates that washing the feet is obligatory.

As for the genitive reading, its meaning is: make your washing of them akin to wiping; do not wash them in a manner that exhausts you. For people, by custom, may wash their feet repeatedly and scrub them, since they are the limbs that come into contact with filth. Custom therefore tends toward washing them excessively. Thus, it appears that the purpose of the genitive reading is to curb people’s habitual excessiveness in washing the feet, because they are the two limbs that encounter filth.

The third explanation is that each of the two readings applies to one of the conditions of the feet. The feet have two conditions:

The first is that they are uncovered, in which case washing them is obligatory.

The second is that they are covered by leather socks or the like, in which case wiping over them is obligatory.

Thus, the two readings are understood in accordance with the two conditions of the feet. The sunnah has clarified this. This is the soundest and least forced of the explanations; it conforms to the principles and to what is known of the Book of Allah Most High, namely that each reading is understood according to a meaning appropriate to it.