Sotah, Chapter Eight, Mishnah Five
Todays mishnah continues explaining the speech made to the troops upon going out to battle. The final exemption is given to anyone who is afraid and disheartened. In our mishnah three rabbis argue what this phrase means.
Then the officers shall go on addressing the troops and say, Is there anyone afraid and disheartened (Deuteronomy 20:8).
1) Rabbi Akiva says: afraid and disheartened is to be understood literally, that he cannot stand in the battle lines and see a drawn sword.
2) Rabbi Yose the Galilean says: afraid and disheartenedthis is the one who is afraid because of the transgressions he has committed; therefore the Torah connected all these [other categories of those who return home] with him that he may return home on their account.
3) Rabbi Yose says: a high priest who married a widow, an ordinary priest who married a divorcee or halutzah, an Israelite who married a mamzeret or netinah, and the daughter of an Israelite who married a mamzer or a natinbehold this one is afraid and disheartened.
Section one: Rabbi Akiva understands the verse literally. The person is literally afraid to go out to battle. He is exempt because his fear may be contagious and cause the other troops to lose heart.
Section two: Rabbi Yose the Galilean understands the exemption as being given to one who has committed transgressions. Assumedly he is afraid that since he has not led a good life, God will not be with him in battle. He notes that the Torah connected this exemption with the others so that the transgressor would not be embarrassed to not go to battle. People seeing him would not know why he is leaving battle and they would assume that he is leaving for one of the other, less embarrassing reasons.
Section three: Rabbi Yose agrees in general with the previous opinion but holds that the transgression must be one that he is continually transgressing, such as a forbidden marriage (the list in this mishnah). If a man is married to a woman forbidden to him, he is transgressing the prohibition every moment he remains married to her. It is only this type of transgression that allows him to leave battle. One who has committed sins in the past is not considered afraid and disheartened.