John Gill Commentary Numbers 13:31

"But the men that went up with him said, We are not able to go up against the people; for they are stronger than we." — Numbers 13:31 (ASV)

But the men that went up with him
With Caleb, all but Joshua: the other ten

said, we be not able to go up against the people ;
this they had not said before, though they plainly suggested it, and, to make the people believe this, had represented the inhabitants of the land of Canaan in the light they did; but now, in direct opposition to Caleb, fully expressed it, giving this reason for it:

for they [are] stronger than we ;
being both of a larger size and more numerous.