John Gill Commentary Numbers 26:65

"For Jehovah had said of them, They shall surely die in the wilderness. And there was not left a man of them, save Caleb the son of Jephunneh, and Joshua the son of Nun." — Numbers 26:65 (ASV)

For the Lord had said of them, they shall surely die in the
wilderness
This was threatened them, (Numbers 14:32) and now it was fulfilled:

and there was not left a man of them, save Caleb the son of Jephunneh,
and Joshua the son of Nun ;
the only two of the spies that brought a good report of the land of Canaan; all the rest of them, and those that murmured on the ill report of theirs, were now dead.