Sahih Muslim Book 20, Hadith Number 4668.

Chapter : The merit of helping the warrior (fighting in the way of Allah) with something to ride upon and looking after his family in his absence.

It has been narrated on the authority of Zaid b. Kbalid al-Juhani that the Messenger of Allah (may peace be upon him) said: Anybody who equips a warrior (going to fight) in the way of Allah (is like one who actually) fights. And anybody who looks well after his family in his absence (is also like one who actually) fights.