Matthew Henry on Numbers 20:14-21

The nearest way to Canaan from the place where Israel encamped, was through the country of Edom. The ambassadors who were sent returned with a denial. The Edomites feared to receive damage by the Israelites. And had this numerous army been under any other discipline than that of the righteous God himself, there might have been cause for this jealousy. But Esau hated Jacob because of the blessing; and now the hatred revived, when the blessing was about to be inherited. We must not think it strange, if reasonable requests be denied by unreasonable men, and if those whom God favours be affronted by men.