Midrash sobre Números 22:7

(Exodus 14:9) "And Egypt pursued them" (This is ostensibly redundant.) We are hereby apprised that not one of them stumbled on the way, lest they resort to divination and turn back. For thus do we find, that these nations resorted to divination, viz. (Devarim 18:14) "For these nations that you are to inherit resort to soothsayers and diviners, etc.", and (Numbers 22:7) "And the elders of Moav and the elders of Midian went, with (instruments of) divination in their hands," and (Joshua 13:22) "And Bilaam the son of Beor the augur they slew by the sword," and the elders of Midian divined and turned back.

8 (Numb. 22:7) “So the elders of Moab and the elders of Midian went with [the tools for] divination in their hand,” for they brought in their hands all kinds of divining instruments through which one divines, so as not to give him an excuse [for not coming]. So the divining instruments were in the hands of the elders of Midian, for they said, “If he comes with us, he will succeed; but if he delays [even] for an hour, he will be of no use.” As soon as they saw that he said (in vs. 8), “Lodge here tonight,” the elders of Midian went away, because they knew through their divinations that he would be of no use.