Albert Barnes Commentary Numbers 13:25

"And they returned from spying out the land at the end of forty days." — Numbers 13:25 (ASV)

After forty days — During this time, they had undoubtedly explored the whole land. However, it was the southern part that the Israelites expected to have to deal with immediately: and accordingly, this is what is particularly referred to in the following verses, Hebron and its vicinity above all.