All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Indeed, it is confirmed in Musnad Ahmad that it was Umm Salamah who asked the Prophet this question, and then the verse was revealed. Nonetheless, it was also confirmed in Sunan At-Tirmithi that it was Umm ‘Umaarah who asked the Prophet this question.
It is most likely that the verse was revealed after they both asked the same question, especially that Umm Salamah mentioned that the verse was revealed after a period of time after she asked the Prophet . In Musnad Ahmad, she said: “I said: O Prophet of Allaah how is it that we are not mentioned in the Quran in the same manner as the men are mentioned?” She said: “Then, one day, I suddenly heard the call of the Prophet on the pulpit while I was combing my hair, and I went near the door [of the room trying to hear what he says] and I listened directly to the voice coming from the direction of the Jareed (i.e. the part of the mosque which was thatched with the dried palm fronds, where the Prophet used to give Khutbah) and I heard him saying: ''Allaah Says (what means): {Indeed, the Muslim men and Muslim women, the believing men and believing women, the obedient men and obedient women, the truthful men and truthful women, the patient men and patient women, the humble men and humble women, the charitable men and charitable women, the fasting men and fasting women, the men who guard their private parts and the women who do so, and the men who remember Allaah often and the women who do so - for them Allaah has prepared forgiveness and a great reward.}[Quran 33:35]
On the other hand, it might be that Umm ‘Umaarah came to ask the Prophet this question and Umm Salamah asked the question on her behalf, so the question was attributed to both of them.
Ibn Katheer mentioned in his Tafseer (interpretation of the Quran) many narrations which were reported by At-Tabari in his Tafseer, among which was what Ibn ‘Abbaas said: “The women asked the Prophet …'', thus he used the plural form of ‘woman’.
Allaah Knows best.