Hadith: Anyone among you stays behind and takes good care of the family and property of a warrior (in the cause of Allah) will receive half the reward of the warrior

عن أبي سعيد الخدري رضي الله عنه أن رسول الله صلى الله عليه وسلم بَعَث إلى بني لَحْيَان، فقال: «لَيَنْبَعِث مِن كُلِّ رَجُلَين أَحَدُهُما، والأجرُ بَينَهُمَا». وفي رواية: «لَيَخْرُجَ مِنْ كُلِّ رَجُلَين رَجُل» ثم قال للقاعد: «أَيُّكُم خَلَفَ الخَارِجَ في أهْلِه وماله بخَير كان له مِثل نِصَفِ أَجْر الخَارجِ».
[صحيح] - [رواه مسلم]

Abu Sa‘īd al-Khudri (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) dispatched a force to Banu Lahyān and said: "Let one of every two men proceed (to join the military force), and both will share the reward." Another narration reads: "Let one of every two men go out (to join the military force)." Then, he said to those who stayed behind: "Anyone among you stays behind and takes good care of the family and property of a warrior (in the cause of Allah) will receive half the reward of the warrior."
Sahih/Authentic. - [Muslim]

Explanation

The Hadīth of Abu Sa‘īd al-Khudri (may Allah be pleased with him) shows that the Messenger of Allah (may Allah's peace and blessings be upon him) wanted to dispatch an army to Banu Lahyān, who were one of the most famous clans of the tribe of Hudhayl. Scholars agreed that Banu Lahyan were disbelievers at that time, so the Prophet dispatched an army to invade them, saying to that army: Let one of every two men proceed to join the military force, which means half the men of every tribe should go. He stated that both the worrier and the one who stays behind to take care of the worrier's family and property will share the reward. This is confirmed in a previous Hadīth that reads: "Anyone stays behind a warrior in the cause of Allah has indeed participated in the raid," and the other explicit Hadīth narrated by Imām Muslim that reads: "Anyone among you stays behind and takes good care of the family and property of a warrior in the cause of Allah will receive half the reward of the warrior". This means that the Prophet (may Allah's peace and blessings be upon him) ordered that one of every two should join the army and the other should stay behind to look after the warrior's family and receive half the reward of the warrior. The other half would be for the warrior himself.