Explanation of the author's statement: "Upon something pure and permissible."

The Shaykh : He said, "If one has a state of ritual impurity after wearing them, while they are upon something pure". Pay attention to the first condition, which is the condition for the permissibility of wiping over leather socks: that it be within the specified time limit. One of the conditions for wiping over leather socks is that it be within the specified time limit, which is one day and one night for a resident and three days for a traveler. Second, that it be upon something pure. Pure is the opposite of impure and soiled. Impure is either impure in itself, such as if the socks are made from donkey skin, in which case they are impure in themselves; or soiled, such as if they are made from camel skin but have been affected by impurity. However, if the soiled item is purified, wiping over it is permissible. But as long as it remains in its state of impurity, it is not possible, because one cannot pray with something that is soiled.