Musnad Ahmad 1156:38

Abu Usamah narrated to us, he said: Hisham narrated to us, from his father, from Zaynab bint Abi Salamah, from Umm Salamah, she said: I said, "O Messenger of Allah, is there a reward for me regarding the sons of Abu Salamah if I spend upon them? And I am not leaving them like this and like this and like this [i.e., scattered], for they are only my sons." He said: "Yes, you have a reward for them for whatever you spend upon them."