Musnad Ahmad 336:1

Abu Sa’id narrated to us, ‘Umar ibn Farrukh narrated to us, he said: Mus’ab al-Ansari narrated to us—I reached him—he said: I reached an old woman of ours who was among those who pledged allegiance to the Prophet, may Allah bless him and grant him peace. She said: We came to him one day, and he took from us the pledge: "That you shall not wail." The old woman said: "O Messenger of Allah, some people had helped me in a calamity that befell me, and now a calamity has befallen them, and I want to help them." Then she came to him and pledged allegiance to him, and she said: "It is the 'ma'ruf' (good/known) which Allah, the Mighty and Majestic, spoke of: {And they will not disobey you in what is ma'ruf} [Al-Mumtahanah: 12]."