Moses
Numbers 31:7BSB·traditional attribution

Then they waged war against Midian, as the LORD had commanded Moses, and they killed every male.

John Calvin Reformed @genevareformer

7. And they warred against the Midianites. It was a signal example of obedience, that 12,000 men did not refuse to engage in a war which was full of danger, when it was reasonable for them to object that it was not right for them to be exposed to butchery, as it were, whilst the people sat idly in the camp, who by their great...

John Gill Reformed Baptist @doctorgill

And they warred against the Midianites, as the Lord commanded Moses,.... Whether the Midianites came out against them with an army, and there was a pitched battle between them, is not certain; however the Israelites committed acts of hostility upon them, by entering their cities, plundering their houses, and slaying the inhabitants of them; the Targum of Jonathan is,"they warred against Midian, and surrounded it...

Jamieson-Fausset-Brown Reformed @jfbcommentary

they slew all the males--This was in accordance with a divine order in all such cases (Deu 20:13). But the destruction appears to have been only partial--limited to those who were in the neighborhood of the Hebrew camp and who had been accomplices in the villainous plot of Baal-peor (Num 25:1-3), while a large portion of the Midianites were absent on their pastoral wanderings or had saved themselves by flight.