מי האיש אשר בנה בית חדש ולא חנכו ילך וישב לביתו פן ימות במלחמה ואיש אחר יחנכנו
An individual whose mind is not on the battle, will – due to his fear or lack of enthusiasm – erode the morale of his comrades. The Torah mentions those individuals who return home and are free from joining the army. These are men who had just initiated an endeavor: taken a wife; built a house; planted a vineyard. For practical reasons, their minds are focused elsewhere – not on the battlefield. Rashi remarks concerning one who has built a house and has yet to move in: He is anxious concerning the possibility that he might die and someone else…
