Sforno on Deuteronomy 20:9/ספורנו על דברים כ׳:ט׳

1ופקדו שרי צבאות, after all those who were sent home had left. If even one of the people that should have been sent home were included in the roll call by the commanders this might eventually prove demoralising if the party in question became a casualty of war. Compare Amos 9,1 הך הכפתור וירעשו הספים, “strike a knob and the very foundations will quake,” [insignificant appearing actions have far-reaching consequences. Ed.]