Sahih Muslim Book 20, Hadith Number 4669.

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.

The above tradition has been narrated on the authority of Khalid al-Juhani who said: The Prophet of Allah (may peace be upon him) said: He who equips a warrior in the way of Allah (is like one who actually fights) and he who looks after the family of a warrior in the way of Allah in fact participated in the battle.