Tirmidhi Book 27, Hadith 1969

حَدَّثَنَا الْأَنْصَارِيُّ، حَدَّثَنَا مَعْنٌ، حَدَّثَنَا مَالِكٌ، عَنْ صَفْوَانَ بْنِ سُلَيْمٍ يَرْفَعُهُ إِلَى النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ:‏‏‏‏ السَّاعِي عَلَى الْأَرْمَلَةِ وَالْمِسْكِينِ كَالْمُجَاهِدِ فِي سَبِيلِ اللَّهِ، ‏‏‏‏‏‏أَوْ كَالَّذِي يَصُومُ النَّهَارَ وَيَقُومُ اللَّيْلَ .

Safwan bin Sulaim narrated that the Prophet said: The one who looks after a widow and a poor person is like the Mujahid in the cause of Allah, or like the one who fasts all the day and stands (in prayer) all the night.