Sotah 44B

שתחילת ניסה נפילה, שנאמר: ״נס ישראל לפני פלשתים וגם מגפה גדולה היתה בעם״, ולהלן הוא אומר: ״וינסו אנשי ישראל מפני פלשתים ויפלו חללים וגו׳״.

because the beginning of fleeing is a downfall on the battlefield, as it is stated: “Israel has fled before the Philistines, and there has been also a great slaughter among the people” (I Samuel 4:17), and likewise it says further on: “And the men of Israel fled from before the Philistines, and fell down slain in Mount Gilboa” (I Samuel 31:1).

במה דברים אמורים ⁠— במלחמות הרשות, אבל במלחמות מצוה ⁠— הכל יוצאין, אפילו חתן מחדרו וכלה מחופתה. אמר רבי יהודה: במה דברים אמורים ⁠— במלחמות מצוה, אבל במלחמות חובה ⁠— הכל יוצאין, אפילו חתן מחדרו וכלה מחופתה.

The Mishnah adds: In what case are all of these statements, with regard to the various exemptions from war, said? They are said with regard to elective wars. But in wars whose mandate is a mitzva, everyone goes, even a groom from his room and a bride from her wedding canopy. R' Yehuda said: In what case are all of these statements, with regard to the various exemptions from war, said? They are said with regard to wars whose mandate is a mitzva. But in obligatory wars, everyone goes, even a groom from his room and a bride from her wedding canopy.

גמ׳ מאי איכא בין רבי יוסי לרבי יוסי הגלילי? איכא בינייהו עבירה דרבנן.

Talmud: The Talmud asks: With regard to their understanding that the “fearful and fainthearted” is referring to one harboring sins, what difference is there between the opinion of R' Yosei and the opinion of R' Yosei HaGelili? The Talmud answers: There is a practical difference between them with regard to a sin which violates a prohibition by rabbinic law. According to R' Yosei HaGelili, one who has violated a rabbinic law returns home, whereas R' Yosei maintains that one returns home only if he has violated a Torah law, as in the case of a priest who has married a divorcée.