Sahih Bukhari Volume 3, Book 34, Hadith Number 279.

Narated By ‘Aisha : The Prophet said, “If a woman gives in charity from her house meals without wasting (i.e. being extravagant), she will get the reward for her giving, and her husband will also get the reward for his earning and the storekeeper will also get a similar reward. The acquisition of the reward of none of them will reduce the reward of the others.”