וַיְמָאֵ֣ן ׀ אֱד֗וֹם נְתֹן֙ אֶת־יִשְׂרָאֵ֔ל עֲבֹ֖ר בִּגְבֻל֑וֹ וַיֵּ֥ט יִשְׂרָאֵ֖ל מֵעָלָֽיו׃ (פ)
Thus Edom refused to give Israel passage through his border; wherefore Israel turned away from him.
Read kabbalistic (mystical) interpretation of Numbers 20:21: and classical mystical sources.