John Calvin Commentary Numbers 14:25

"Now the Amalekite and the Canaanite dwell in the valley: to-morrow turn ye, and get you into the wilderness by the way to the Red Sea." — Numbers 14:25 (ASV)

Now the Amalekites and the Canaanites. Some interpret these words as follows: “Although the Amalekites dwell in the valley.” Others understand them this way: “Since the Amalekites remain in the valleys to lay ambushes.” Still others think their purpose is to inspire terror, so that the Israelites would not remain too long in the enemy’s territory, as they would be exposed daily to new attacks.

However, I am more inclined to believe that these words are spoken as a reproach. For the Israelites had already reached the borders of the inhabited land, so their enemies could have been routed at once. But instead, God commands them to retreat, thereby expelling them from the land they had, in fact, reached.

Nevertheless, I do not deny that God also presents them with the necessity of the situation, thereby enforcing their obedience, as if He had said that nothing now remained but to retreat and throw themselves into the desert again.