Musnad Abu Ya'la al-Mawsili 155:251

Abu Bakr narrated to us, Hafs narrated to us, from Talq ibn Mu'awiyah, from Abu Zur'ah, from Abu Hurayrah, who said: A woman came with a young son of hers and said, "O Prophet of Allah, supplicate to Allah, supplicate to Allah, for I have buried three." He said, "You have buried three?" She said, "Yes." He said, "You have indeed fortified yourself with a strong fortification against the Fire."