Abu Hurairah reported,
The Messenger of Allah ﷺ said, "The one who strives to support the widow and the poor is like the Mujahid in the path of Allah 
."
Nasai 2578
Sahihأخبرنا عمرو بن منصور قال حدثنا عبد الله بن مسلمة قال حدثنا مالك عن ثور بن زيد الديلي عن أبي الغيث
عن أبي هريرة قال
قال رسول الله ﷺ الساعي على الأرملة والمسكين كالمجاهد في سبيل الله عز وجل
Bukhari narrated it in the Book of Manners, chapter on one who strives on behalf of the poor, hadith no. 6007, and Muslim narrated it in the Book of Asceticism and Softening of Hearts, chapter on the merit of kindness to the widow, the poor, and the orphan, hadith no. 2982, from Abdullah bin Maslama Qanabi, with this same wording. It is also found in al-Kubra, hadith no. 2358, and in Muwatta, narrated by Abu Musab Zuhri Madani, 2/86–87, hadith no. 1916.