3 And he shall say to them, 'Hear, O Israel: Today you are on the verge of battle with your enemies. Do not let your heart faint, do not be afraid, and do not tremble or be terrified because of them;

Matthew Henry's Commentary on Deuteronomy 20:3

Commentary on Deuteronomy 20:1-9

(Read Deuteronomy 20:1-9)

In the wars wherein Israel engaged according to the will of God, they might expect the Divine assistance. The Lord was to be their only confidence. In these respects they were types of the Christian's warfare. Those unwilling to fight, must be sent away. The unwillingness might arise from a man's outward condition. God would not be served by men forced against their will. Thy people shall be willing, Isaiah 8:12.