Surah al-Mujadilah (The Contention) 58 : 6

There is no hadith to tell as to when this incident of pleading and arguing took place, but there is a hint in the subject matter of the Surah on the basis of which it can be said with certainty that it happened sometime after the battle of the Trench (Shawwal, 5 A.H.). In Surah 33: al-Ahzab (The Confederates), God while negating that an adopted son could be one’s real son, had just said this and no more; “And God has not made those of your wives whom you divorce by dhihar your mothers.” But in that Surah there was nothing to the effect that to divorce a wife by dhihar was a sin or a crime, nor anything about the legal injunction concerning it. Contrary to it, in this Surah the whole law relating to dhihar has been laid down, which shows that these detailed injunctions were sent down some time after the brief reference to it in Surah 33: al-Ahzab (The Confederates).