The twelve spies return NUM 13:26

All twelve agreed the land was fertile, and they showed it by carrying back the cluster of grapes. But ten of them focused on the fortified cities and the giant inhabitants and concluded the land could not be taken, while Caleb and Joshua, looking at the same evidence, urged going up at once.

Kadesh Barnea was the wilderness camp from which the spies set out and to which they returned, right on the edge of Canaan. It was there that the congregation made its decision not to go up, which is why the place became a lasting symbol of hesitating at the threshold of the promise.

The forty years follow from the congregation choosing to believe the fearful report of the ten spies rather than the confidence of Caleb and Joshua. That refusal to trust meant the generation that left Egypt would not enter the land, and the wilderness years stretched out as a result, as the rest of the passage describes.

All twelve spies agreed on the facts: the land was good, the cities were walled, and the people were large. The disagreement was over what to conclude from that - ten judged defeat to be certain, while Caleb and Joshua judged victory to be possible, a difference some readers understand as a matter of nerve rather than of observation.