Because the LORD was not able to bring this people into the land which he swore to give unto them, therefore he has slain them in the wilderness.
Read Chapter 14
George Leo Haydock
Sworn. God swore to give this land to the Hebrews, but not to this particular generation. His oath would be equally fulfilled by raising posterity to Moses, ver. 13. But, at his entreaty, he spared the descendants of this people, and gave the land to their children under Josue. (Haydock)