Sahih Muslim Book 42, Hadith Number 7107.

Chapter : Benevolent Treatment to the Widows, Orphans, the Poor.

Abu Huraira reported that Allah’s Messenger (may peace be upon him) said: One who makes efforts (for earning to be spent) on a widow and the destitute is like a striver in the cause of Allah, and I think he also said: He is like one who constantly stands for prayer and observes fast without breaking it.