It is established in the sunnah that Ibn Masud, may Allah be pleased with him, was asked about a man who married a woman but did not consummate the marriage with her, then died. He said: “She must observe the waiting period, and she is entitled to the bridal gift and inheritance.” Then a man stood up and said: “The Prophet, peace and blessings be upon him, ruled concerning Barwa bint Washiq—a woman from among us—in the same way that you have ruled.” (1) Thus, Ibn Masud ruled that she must observe the waiting period even though he had not consummated the marriage with her.

A free woman must observe a waiting period of four months and ten days, while an enslaved woman observes half of that. If the husband of a revocably divorced woman dies while she is still observing the waiting period for divorce, that waiting period ceases, and she begins the waiting period due to death from the time of his death, …

His statement, “A free woman must observe a waiting period of four months and ten”: the word “ten” is in the feminine form, since the counted noun is masculine. However, it has previously been explained that, with the numbers three through ten, the number takes the feminine form with a masculine counted noun and the masculine form with a feminine one when the counted noun is explicitly mentioned. When it is not mentioned, however, either form is permissible.

Accordingly, the saying of Allah, Most High, “Divorced women shall wait by themselves for four months and ten,” does not mean ten nights—as many scholars have said—but rather ten days. This is because “months” denotes daytime duration, and thus the ten likewise refers to days. Yet the number was not put in the feminine form, because it is not obligatory for the number to agree in gender with the counted noun unless that noun is explicitly mentioned. Thus, a free woman observes a waiting period of four months and ten days. The evidence is the saying of Allah, Most High:

“And those of you who die and leave wives behind, they shall wait by themselves for four months and ten days.” [al-Baqarah: 234]

The wisdom in making it four months and ten days—and Allah knows best—is that it safeguards the right of the first husband. Hence, because the right of the Messenger, peace and blessings be upon him, was especially great, his wives were forbidden in marriage to the Ummah for their entire lives. As for others, four months and ten days suffice. Why, then, are they four months and ten days?

The answer is that four months are one-third of a year, and ten days are one-third of a month, and