The spies executed their mission faster than expected because God had mercy on the Israelites and sought to abbreviate the duration of their punishment.

The verse states concerning the spies: “They returned from scouting the land at the conclusion of forty days” (Numbers 13:25). But don’t you find that they traveled south to north in forty days? How did the entire mission last forty days? It was revealed before the Holy One, Blessed be He, that they would come and slander the land, and it would be decreed against that generation that they would endure years of suffering, “each day for a year” (14:34). And the Holy One, Blessed be He, shortened the way before them.