Sforno on Numbers 22:7/ספורנו על במדבר כ״ב:ז׳

1וקסמים בידם, the instruments by means of which to perform sorcery.. Bileam’s specific expertise in such sorcery was to calculate precisely when certain constellations would be favourable to what he planned to achieve. He is described as a sorcerer when his death his reported in Joshua 13,22.