with whom you have consummated marriage”—and the rest of the verse—and in His words, Exalted is He:

“Do not marry women whom your fathers married, except what has already passed.”

The Companions, the Successors, and all the other imams of the religion said that the condition applies only to stepdaughters. They said: “Leave unrestricted what Allah has left unrestricted.” What is left unqualified is unrestricted, whereas what is subject to a condition is delimited and restricted. Thus, wives’ mothers and the wives of fathers and sons become forbidden in marriage through the marriage contract alone, whereas stepdaughters become forbidden only when marriage with their mothers has been consummated. However, scholars disagreed over whether death has the same effect as consummation; there are two opinions within Ahmad’s school.

This is because the rulings differ, and the restriction does not apply identically to the persons concerned. Prohibiting one category is not the same as prohibiting another, different category. Similarly, blood, carrion, and swine’s flesh belong to different categories: restricting the prohibition of blood to blood that has been shed does not entail applying that same restriction to carrion and swine. Here, the restriction is that marriage with the stepdaughter’s mother must have been consummated. Consummation with the mother has no exact counterpart in the cases of fathers’ and sons’ wives or a wife’s mother: in the case of a wife, consummation is with the woman herself, whereas in the case of a wife’s mother, it is with her daughter.

Likewise, the Muslims did not interpret unrestricted wording in light of restricted wording concerning the required number of witnesses. Rather, when Allah mentioned two men, or one man and two women, in the verse on debt, and two men for taking back a divorced wife, they retained each prescription as it stood. This is because the basis of the ruling differs—property in one case and marital relations in the other—and this difference affects the required number of witnesses.

Similarly, four witnesses are required in connection with enforcing the prescribed punishment for sexual immorality and with accusations of it; the contracting of oaths and marriages is not to be judged by analogy with that. He mentioned three rulings concerning the prescribed punishment for accusations of sexual immorality: