Sforno on Numbers 13:28/ספורנו על במדבר י״ג:כ״ח

1אפס כי עז העם, it is impossible to conquer the land since we cannot defeat its people. Not only are the people tough, but the cities are fortified. The inhabitants of the land, the Amelakites hate us fiercely. They will engage in a preemptive war against us so that we should not even get near their borders.