Musnad Abu Ya'la al-Mawsili 209:130

Abu Khaythama narrated to us, Ya'qub ibn Ibrahim narrated to us, my father narrated to us, from Ibn Ishaq, who said: Hisham ibn 'Urwah narrated to me, from his father, from Zaynab bint Abi Salamah, from her mother, Umm Salamah, who said: I said to the Messenger of Allah (peace and blessings of Allah be upon him): "O Messenger of Allah, is there a reward for me regarding the sons of Abu Salamah? For I spend on them, and they are my sons, and I will not leave them like this and like that." She said: "Whether I have a reward or not." He (peace and blessings of Allah be upon him) said to me: "Yes, you have a reward for them for what you spend on them."