narrated safwan bin salim (radi-allahu 'anhu):
the prophet (sallallahu 'alaihi wa sallam) said "the one who looks after and works for a widow and for a poor person, is like a warrior fighting for allah's cause or like a person who fasts during the day and prays all the night." narrated abu huraira that the prophet (sallallahu 'alaihi wa sallam) said as above.
bukhari vol. 8 : no. 35