According to the number of days in which you spied out the land [of Canaan], forty days, for each day, you shall bear and suffer a year for your sins and guilt, for forty years, and you shall know My displeasure [the revoking of My promise and My estrangement because of your sin].

When they returned from spying out the land, at the end of forty days,

Your sons shall be wanderers and shepherds in the wilderness for forty years, and they will suffer for your unfaithfulness (spiritual infidelity), until your corpses are consumed in the wilderness.

So the Lord’s anger was kindled against the sons of Israel (Jacob) and He made them wander in the wilderness forty years, until the entire generation of those who had done evil in the sight of the Lord was destroyed.