Only that the generations of the children of Israel might know, to teach them war, at least those who before knew nothing thereof;
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George Leo Haydock
AD 1849
And be. Hebrew, "at least, such as before knew nothing thereof. "Though war be in itself an evil, the passions of men render it necessary, and God makes use of it as a scourge, to punish the wicked, and at the same time to keep all under due restraint. (Haydock)
Too long a peace has proved sometimes fatal to states and to the virtue of individuals. In adversity we call upon God, and adhere to him with greater fervour and constancy. The Jews were so prone to evil, that, if they were permitted to enjoy tranquility for a few years, they presently forgot themselves and the author of all their good, and even turned their backs upon the only true God. Their enemies forced them to have recourse to Him. (Calmet)