such a type of headwear may not be wiped over, because the basic rule is that the head must be wiped, as Allah Most High says: “Wipe your heads” [al-Māʾidah 5:6].

An exception to this basic rule was made for the turban because of the textual evidence concerning it.

Some of the scholars of the school said: One may wipe over caps if they are like a turban and difficult to remove (1). As for what is not difficult to remove, such as the familiar skullcap, one may not wipe over it. Thus, they differentiated between what is difficult to remove and what is not.

This view is strong, for the Lawgiver does not differentiate between equivalent cases, just as He does not treat differing cases alike (2). For the Sacred Law comes from One Who is All-Wise, All-Knowing, and matters are judged according to their underlying meanings, not their outward forms.

Since the Sacred Law has permitted wiping over the turban, everything that resembles it in the difficulty of removing it is given the same ruling.

Nor may one wipe over a foot wrapping, …

His statement, “Nor [may one wipe over] a foot wrapping,” means a wrapping on the foot. Thus, a person may not wipe over a cloth that he has wrapped around his foot, because it is not a leather sock and therefore does not fall under its ruling.

In earlier times, people lived in poverty and hardship and could not find leather socks. A person would therefore take a piece of cloth, wrap it around his foot, and then tie it.

The reason it is not permissible is that the basic rule is the obligation to wash the foot. This basic rule was excepted in the case of the leather sock because of the textual evidence concerning it; whatever else remains is therefore subject to the basic rule.