Deuteronomy 20:7
And what man is there that hath betrothed a wife, and hath not taken her? let him go and return unto his house, lest he die in the battle, and another man take her. And what man is there that hath betrothed a wife, and hath not taken her? let him go and return unto his house, lest he die in the battle, and another man take her.
A man who had become engaged to marry but had not yet taken his wife was to leave the army and return to his house before battle. He was sent home so that he might marry her, lest he die in the battle and another man take her in his place. This requirement stands as one of the pre-battle exemptions by which men with unfinished personal responsibilities were allowed to leave the army.
The exemption expresses tender care for family ties, so that no man would be forced into battle against his will while such a bond remained uncompleted. In Gideon's case the usual proclamation of these exemptions was not made, because his force was already small.
The same direction embodies the principle that those whose private interests would draw their hearts away from God's work were to return home. Those absorbed in private concerns should likewise step aside from that work rather than weaken it by their example.