As for their proof from the Book, it is the Almighty’s statement: “Those of your women who have despaired of menstruation—if you are in doubt—their waiting period is three months; the same applies to those who have not yet menstruated” (65:4). Here the waiting period is fixed in months only when there is no menstruation, which shows that the original rule is to calculate it by menstrual cycles and that the months serve merely as a substitute when menses are absent.
Their proof from the Sunnah is the hadith that a bond-woman observes two menstrual periods as her waiting time, and the hadith, “Refrain from the prayer during the days of your qurūʾ (menses).” You will, God willing, find a full treatment of this question and the evidence marshalled by both sides under Sūrah al-Baqarah. We have already indicated that, in our judgment, reckoning the periods of purity is the weightier view, because its Qur’anic verse is clearer and the hadith that explicitly supports it is more authentic.
An illustration of the third category of issues we mentioned earlier is our explanation that the agent in the passive reading of His words, “How many a prophet was fought alongside by ribbiyyūn” (3:146), is the plural noun ribbiyyūn and not a pronoun referring to the prophet himself. The proof is His declaration: “Allah has decreed: ‘I and My messengers shall indeed prevail’” (58:21) and other similar verses. For if we were to take the agent as a pronoun for the prophet, this would imply that many prophets were killed on the battlefield, as the construction ‘how many (wa kaʾayy-in)’ entails. Yet Allah’s explicit assertion that He has decreed victory for Himself and for His messengers totally excludes such a reading. Moreover, He says: “Messengers before you were indeed denied, yet they patiently bore the denial and the harm until Our help came to them; none can change the words of Allah” (6:34). The phrase “none can change the words of Allah” plainly affirms that the messengers’ triumph is unalterable, for their victory over their opponents is exactly what the divine word “I and My messengers shall indeed prevail” conveys. Without doubt, then, this is one of His irrevocable words, as al-Qurṭubī and others have noted. He has further negated, in absolute terms, any possibility that one aided by Allah could be overcome: “If Allah supports you, none can overpower you” (3:160).