Albert Barnes Commentary Exodus 18:5

"And Jethro, Moses` father-in-law, came with his sons and his wife unto Moses into the wilderness where he was encamped, at the mount of God:" — Exodus 18:5 (ASV)

The wilderness - that is, according to the view which seems on the whole most probable, the plain near the northern summit of Horeb, the mountain of God. The valley which opens upon Er Rahah on the left of Horeh is called “Wady Shueib” by the Arabs, that is, the valley of Hobab.