Numbers 31:3-5

Young's Literal Translation

³ And Moses speaketh unto the people, saying, `Be ye armed some of you for the host, and they are against Midian, to put the vengeance of Jehovah on Midian;

⁴ a thousand for a tribe -- a thousand for a tribe, to all the tribes of Israel -- ye do send to the host.'

⁵ And there are given out of the thousands of Israel a thousand for a tribe, twelve thousand armed ones of the host;