Midrash sobre Números 31:4

(Numb. 31:4) “[You shall send to the war] a thousand per tribe [from all the tribes of Israel]”: Some say, “He sent two thousand from each and every tribe.” But others say, “Three thousand from each and every tribe, [with twelve thousand fighters], twelve thousand to guard the baggage, and about them it is stated (in Cant. 4:2), ‘Your teeth are like a flock of ewes that are perfectly matched’; and twelve thousand for prayer.” And where is it shown? Where it is stated (ibid.), “A thousand per tribe (literally, a thousand per tribe; a thousand per tribe).” That is twenty-four thousand. (Numb. 31:5) “So from the thousands in Israel there were furnished a thousand per tribe.” That is twelve thousand others. What is the meaning of “were furnished?” That they were furnished for each other in pairs.⁴Gk.: zeuge, zuga; Lat.: jugera. The probable meaning is that for each thousand who fought, there were a thousand replacements. Another interpretation [of “were furnished”]: They were furnished by force. Since Scripture had made the death of Moses dependent upon the vengeance against Midian, they said, “Shall we go against Midian and let Moses die?” They refrained from going. The Holy One, blessed be He, said to Moses, “Cast lots over the tribes, and they will be furnished automatically.”

(Bamidbar 31:4) "A thousand to a tribe, a thousand to a tribe": 24,000 all together, viz. (Ibid. 5) "And there were handed over … twelve thousand armed for the host, etc." R. Akiva says: "a thousand to a tribe, a thousand to a tribe." Why (add) "And there were handed over, etc." To exclude the tribe of Levi. "And there were handed over of the thousands of Israel": Scripture hereby apprises us that they were just and righteous men, who gave of themselves for the cause. R. Nathan says: Others handed them over: "This man is kasher — Let him go! This man is a tzaddik — Let him go!" R. Elazar Hamodai says: Come and see the love (of Israel for) the shepherd of Israel. So long as they had not heard that the death of Moses was attendant upon the war with Midian, what is written of them? (Shemot 17:4) "Just a little more and they will stone me." When they heard of it, they began hiding (to avoid conscription, so as not to be instrumental in his death) — notwithstanding which they were conscripted perforce, viz. "And there were handed over of the thousands of Israel, etc."