Sahih Bukhari Volume 002, Book 024, Hadith Number 546.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 24. Obligatory Charity Tax (Zakat)
Narated By Zainab, : (The daughter of Um Salama) My mother said, "O Allah's Apostle! Shall I receive a reward if I spend for the sustenance of Abu Salama's offspring, and in fact they are also my sons?" The Prophet replied, "Spend on them and you will get a reward for what you spend on them."