Musnad Ahmad 904:2

Yazid narrated to us, Hisham informed us, from Muhammad, who said: A woman used to come to us who was called Mawiyah narrated to us. She used to suffer the loss of her children. She came to Ubayd Allah ibn Ma'mar al-Qurashi, and with him was a man from the companions of the Prophet, may Allah bless him and grant him peace. That man narrated that a woman came to the Prophet, may Allah bless him and grant him peace, with a son of hers. She said: "O Messenger of Allah, supplicate to Allah that He may keep him for me, for three [children] of mine have died before him." The Messenger of Allah, may Allah bless him and grant him peace, said: "Since you have accepted Islam?" She said: "Yes." The Messenger of Allah, may Allah bless him and grant him peace, said: "A fortified shield." Mawiyah said: Ubayd Allah ibn Ma'mar said to me: "Listen, O Mawiyah." Muhammad said: "So Mawiyah left from the presence of Ibn Ma'mar, and she came to us and narrated this hadith to us."