Balaam also, the son of Beor the soothsayer, did the children of Israel slay with the sword,.... At the same time that the princes of Midian were slain, and which is also observed, See Gill on "Nu 31:8".
Kimchi supposes that he returned to Midian, on hearing that the counsel he gave to them, to ensnare Israel with their daughters, had taken effect, in order to receive his wages, and so received his righteous doom and just reward; it is commonly said by the Jews , that he was slain by Phinehas:among them that were slain by them; among the above princes, and the common soldiers, of which there was a great slaughter; even all the males of Midian were slain, Nu 31:7.
T. Bab. Sanhedrin, fol. 106. 2.