Deuteronomy 2:1

Ver. 1. And we compassed mount Seir— The meaning is, they spent near thirty-eight years in the encampments and slow marches made in the wilderness, which lies round the south and west borders of the country of Edom, into which they had not hitherto entered, ver. 4. By mount Seir is meant the mountainous part of Edom, or Idumea. The whole country of Edom, in the times of the kings, reached from the confines of Canaan unto Ezion-gaber on the Red Sea; 1 Kings 9:26. On which account the Arabian gulf was called the sea of Edom, or the Red Sea; but in Moses's time, the land of Edom appears to have been of a much smaller extent, reaching no further south than mount Hor, which is said to have been in the edge of the land of Edom. It was at the end of the thirty-ninth year after their coming out of Egypt that the Lord spake unto Moses, as mentioned in the second and following verses. See Dr. Shaw's Travels, p. 320.