I think the earliest considerations regarding this was from St. Paul, who like the other protagonists of the New Testament (John the Baptist, Elizabeth and Zachary; Jesus, Mary and Joseph; the apostles and the first Christians) come from firstborn Israel. Romans 9-11 would be St. Paul's reflections regarding this.

St. Paul did relate Sinai with 'Arabia' in Gal 4:25. But this is not the equivalent of today's Saudi Arabia or Arabian Peninsula, but the slightly different territory of the Nabatean kingdom (later conquered by the Roman empire and called 'Arabia Petraea'). As you can see in the map, 'Arabia'/Nabatea back then included the modern-day Sinai Peninsula (it wasn't part of ancient Egypt at the time). Ancient Egypt bordered with ancient Nabatea, including the Sinai peninsula; besides, back then Sinai should be outside of (and not too far from) Egypt because the Israelites had to 'go out of Egypt' to Sinai in order to sacrifice to the Lord (cf. Ex 3:12).

Bridegroom of Blood

In the grandeur of God’s plan, we can easily miss one little verse: “At a lodging place on the way the Lord met him [Moses] and sought to kill him” (Ex 4:24). But Zipporah, his wife, took out a flint knife, cut off her son’s foreskin, touched Moses’ feet with it and said, “You are a bridegroom of blood to me!” So the Lord relented (v. 25).

God, the assassin? So which way is it? We had the impression that you wanted to use Moses to liberate your people, and now you’re trying to exterminate him before he ever crosses the border? What was going on? Once again, we need to understand Scripture from the perspective of Hebrew signs and symbols, their family heritage. Moses was in fact a covenant breaker because Gershom, his firstborn, was uncircumcised. When God had instituted circumcision in his covenant with Abraham several generations before, he had told Abraham, “If any man refuses to circumcise his son in eight days, I shall cut him off like so much foreskin” (Gn 17:10-14).

Why hadn’t Moses kept the covenant? The Midianites did practice circumcision, but like the Ishmaelites, they followed the custom that many Arabs practice down to the present time. Arabs perform circumcision around the age of thirteen (as with Ishmael), as a rite of passage from boyhood to manhood. On the other hand, the Israelites were to follow God’s command given to Abraham concerning Isaac, by circumcising their male infants on the eighth day, a statement of acceptance by God into the family covenant that did not depend upon their future “manliness.”

Maybe Moses excused himself by saying, When in Midian, do as the Midianites do. After all, I don’t want to offend Jethro, my father-in-law, who also happens to be a priest of Midian.

Evidently, Moses had offended his Father, so seriously that God tried to kill him. He was showing Moses that he meant business when he talked about breaking the covenant: “When you break the covenant, you rupture my family.”

Moses is spared only because his Midianite wife circumcised Gershom and touched her husband’s feet with the bloody foreskin. Since Zipporah knew exactly what to do, we may suppose that she was aware of the specific obligation her husband had neglected. In short, the severity of God’s response may indicate sufficient knowledge on both their parts. In any case, Zipporah’s response averted disaster; her important role in God’s redemptive plan for his family should not be overlooked.