Sahih Muslim Book 5, Hadith Number 2190.

Chapter : Getting of reward to Sadaqa for the dead given on his or her behalf.

Umm Salama said: I asked the Messenger of Allah (may peace be upon him) whether there is a reward for me if I spend oh Abu Salama’s sons, and I am not going to abandon them in this state (of helplessness) for they are my sons. He (the Holy Prophet) said: Yes. For you is the reward for what you spend on them.