Targum for Numbers 20:21

So Edomea would not suffer Israel to pass through his coast; and Israel turned away from him, because it was commanded from before the Word of the Heavens that they should not set battle in array against them, forasmuch as the time was not yet come when the punishment of Edom should be given into their hands.

And Israel turned away from them; for so was the commandment of their Father who is in heaven, that they should not set against them the array of war.