Charles Ellicott 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)

Where he encamped at the mount of God. — It is quite possible that “the mount of God” may be here used, in a broad sense, of the entire Sinaitic mountain-region, as “wilderness” is just before used in the broad sense of the infertile region between Egypt and Palestine. Or the movement described in Exodus 19:1-2 may have taken place before Jethro’s arrival, though not related until after it. We must bear in mind that Exodus was probably composed in detached portions, and arranged afterwards. The present chapter has every appearance of being one such detached portion.