Mus'ab bin Nuh Ansari says that I found an old woman who was among the women who pledged allegiance to the Prophet (peace be upon him). That woman said that one day we presented ourselves before the Prophet (peace be upon him), and he took a promise from us that we would not wail (over the dead). I said, "O Messenger of Allah! On one occasion, I was afflicted with a calamity and some people helped me in it. Now, if a calamity befalls them, I wish to help them." Then I came and pledged allegiance to the Prophet (peace be upon him). That woman said that this is the "ma'ruf" (good deed) about which Allah has said: "And that they will not disobey you in what is right" .