92 It would take too long to go through all the wars of Moses. It is enough to refer to what has already been said, as sufficient for the purpose in this reply to Faustus of the prophetic and symbolic character of the war with Amalek. There is also the charge of cruelty made against Moses by the enemies of Scriptures, or by those who have never read anything. Faustus does not make any specific charge, but speaks of Moses as commanding and doing many cruel things. But, knowing the things they are in the habit of bringing forward and of misrepresenting, I have already taken a particular case and have defended it, so that any Manichæans who are willing to be corrected, and all other ignorant and irreligious people, may see that there is no ground for their accusations.
We must now inquire into the prophetic significance of the command, that many of those who, while Moses was absent, made an idol for themselves should be slain without regard to relationship. It is easy to see that the slaughter of these men represents the warfare against the evil principles which led the people into the same idolatry. Against such evil we are commanded to wage war in the words of the psalm, "Be angry and sin not." And a similar command is given by the apostle, when he says, "Mortify your members which are on earth fornication, uncleanness, luxury, evil concupiscence, and covetousness, which is idolatry."
Source: Reply to Faustus the Manichaean (New Advent)