Behold, these, on Balaam's advice, caused the people of Israel to act treacherously against YHWH in the incident of Peor, and so the plague came among the congregation of YHWH.
#numbers 31:16

The Doctrine of Balaam is the luring of God's people into idolatry and other pagan practices, primarily through hedonism, the pursuit of pleasure. There's nothing inherently wrong with the pursuit of pleasure (or happiness, if you prefer), but passions are easy to manipulate into weaknesses and blind spots.