Rashi on Deuteronomy 1:40/רש"י על דברים א׳:מ׳

1פנו לכם TURN YE — I thought to let you pass across the breadth of the land of Edom in a northerly direction and thus enter the Land (cf. Rashi on Numbers 34:3); you, however, became degenerate and caused this delay for yourselves.

2פנו לכם TURN YE backwards, and proceed through the wilderness towards the Red Sea; — for the wilderness through which they were travelling was to the south of Mount Seir separating the Red Sea from Mount Seir. — Now proceed in the direction of the Sea and travel round Mount Seir along the whole of its south side from the west to the east.