Most focus on the clear teaching that Moses married Zipporah, a Midianite, during his 40 years in the wilderness (having fled from the presence of Pharaoh). Zipporah was rejoined with Moses early on the Exodus (see Exodus 2:16-22; 18:2-6).
In Numbers 12:1, Moses wife became the apparent reason for Miriam and Aaron's rebellion against Moses.
Here Moses is said to have a wife that is Cushite. This sets the stage for much speculation, including the idea that Moses had two wives. Let's examine the possibilities and factors which weight into any determination.
Midianites predominately came from the eastern side of the Gulf of Aqabah (in the modern area of Saudi Arabia). Midianites are referred to as shepherds and traders or merchants in the Old Testament (See Genesis 37:28; Exodus 2:16-17). Midian and Moab, to its north, were allied (Numbers 22:4, 7). The Midianites were part of Moab's attempts to corrupt Israel (Numbers 25:1-9). The Midianites were subsequently treated as enemies of Israel (Numbers 31:1-8).
Cushites were from the area of the kingdom of Kush, directly to the south of Egypt, also known as the Nubian kingdom of Napata (or the Napatan Kingdom) in the Egyptian New Kingdom period, present day Sudan. Cushites, or Nubians, are perhaps best known for the beautiful exceedingly black skin color. (Many translators wrongly associate the Cushites with Ethiopia. See also www.notjustanotherbook.com/queencandace.htm).
Three possibilities for consideration:
#1. Moses had two wives (simultaneously)
Some articles on polygamy actual presuppose this to be fact (For example statements such as "Many important figures had more than one wife, such as... Moses..." and "Polygamists in the Bible: Moses").
While this is a possibility and one that was shown to occur in Israel's history (consider Abraham, Jacob, Esau, Gideon, David, Solomon), it is the least likely scenario for consideration in regards to Moses. The Law certainly allowed for this and provided legal protections for all involved (see Exodus 21:10; Deuteronomy 21:15-17; even Deuteronomy 17:17). And yet, by positive example, from the very beginning God showed that His plan for marriage was to be one man with one woman. This is why examples of polygamist marriage normally showed the problems that arose from this less than perfect practice. Had Moses had multiple wives it would be out of character to the Bible's portrayal of such marriages that the problems stemming from such would not be highlighted or in view at all. And, since the Law and earlier practice of Israeli patriarchs allowed for multiple marriages, this cannot be construed as the reason Miriam and Aaron were upset with Moses.
The ancient historian Josephus, writing in the first century A.D., tells us a fanciful story regarding Moses in an apparent attempt to give reason for Moses' Cushite wife. Some feel that Josephus drew on the work of one Artapanus of Alexandria, a man of Jewish origin, who lived circa the 2nd century B.C., who composed history for a public audience in Egypt. In other words, he too crafted his history for the masses and, from what excerpt we have, he most certainly manipulated it to impress his pagan audience.
In summary, in Josephus' account, in Moses' early adult life, he had led the Egyptians in a campaign against invading Ethiopians and defeated them. While Moses was besieging the city of Meru, princess Tharbis watched him lead the Egyptian army from within the city walls, and fell in love with him. He agreed to marry her if she would engineer the deliverance of the city into his power. She did so immediately and Moses promptly married her. After the war, she returned to Egypt with Moses. End Note (FYI, the early church father Irenaeus, who lived 130-202 A.D., was familiar with this story regarding Moses. Hollywood carried the legend of Tharbis into recent times through Cecil B. DeMille's 1956 epic The Ten Commandments.)
Josephus, and likely his source, got the history wrong in this crafted story. The Ethiopians were not the kingdom of Cush. In fact, naming the city "Meru" was likely taking more recent Egyptian history, using the capital of the then extant capital city of the later Kingdom of Cush, namely Meroe, and ascribing it to Ethiopia. In Moses' day, Napata was the capital city of the Kingdom of Cush.
Interestingly, anyone who accepted this account held that Moses was already married to Tharbis, his Cushite wife, before Moses fled to Midian and later married Zipporah. The account presupposes a polygamist marriage with Zipporah being the second wife. At the same time, it gives no reasonable reason for my Aaron and Miriam would have been upset with Moses for marrying "the Cushite" and why it would become an issue later in the Exodus.
#2. Moses' Midianite wife was of Cushite ethnicity
Some have tried to speculate that the later reference to Moses' wife as being a Cushite was still in reference to Zipporah. They sometimes refer to the parallel of this minor prophet:
While the word Cushan is similar in Hebrew, perhaps having common root, it is a different word and likely references a place in the Arabian Peninsula near or part of Midian. Clearly Zipporah is portrayed as being from the Midianite family of Jethro (Exodus 3:1; 18:5) or Reuel (Exodus 2:18; Numbers 10:29).
Others hypothesize that Zipporah's family may have been Cushite immigrants to the Midian region, but it would be highly improbable that a foreigner would have been "priest of Midian (Exodus 3:1). Midian and Kush are quite separated geographically and there is no historical evidence suggesting any close relationship that would have provided a setting for such immigration.
Still others suppose that the Cushite reference was only a (perhaps derogatory) reference to her dark skin color, suggesting the people of the Arabian Peninsula perhaps had darker skins. This is improbable as many Egyptians would have had darker skins as well (shown by artifacts and paintings from the New Kingdom) and both the Egyptians and Midianites never had skin colors approaching the incredibly beautiful dark ebony of the Nubian peoples of Kush.
And, if this reference was to Zipporah, whether in regards to her skin color or ethnicity, it is somewhat remarkable that Aaron and Miriam's displeasure would begin so late. They certainly would have lots of time to have expressed it previously on the Exodus.
A poet/playwright from perhaps the second century B.C., who lived in Alexandria Egypt, called Ezekiel the Tragedian, wrote a drama retelling the biblical story of the Exodus. Parts of his narrative were clearly altered to suit the needs of his play. In his poetic retelling, he has Zipporah describing herself as a stranger in Midian with her people's ancestral lands being in North Africa. This ancient work shows that such speculations regarding Zipporah have existed for some time and that people should not base their belief in ancient dramatic poets any more than modern Hollywood (as evidenced by the 2014 Exodus: Gods and Kings).
#3. Moses had two wives (successively)
As Zipporah is never again mentioned (chronologically) in the text, it is quite logical to assume Moses' Midianite wife had died and Moses had now, shortly after, married another woman who was Cushite.
Miriam and Aaron's reason for being upset with Moses may have hinged on two factors:
A.The minimal timeframe after Zipporah's death (the fact she was Cushite being a detail twice provided to show that she was a new wife who was not Midianite). And yes, it is an assumption that Zipporah died. It is also possible that Moses divorced her - divorce too was permitted under the Law (though, again, not part of God's perfect design). If divorce was in view, Moses and Aaron may have been upset of Moses soon remarriage after the divorce. I find this latter speculation, concerning a possible divorce, improbable. Divorce, though permitted (Matthew 19:8), was normally portrayed in a negative light throughout the Old Testament and it would be out of character for the text to not display this. God's subsequent vindication of Moses, in the face of Miriam and Aaron's displeasure, implies that Moses had done not wrong in the circumstances leading to their actions. As can be seen throughout the Old Testament, God is normally quite willing to call out leaders for the wrong actions, either directly or through those around them. Zipporah's death can be reasonably assumed.
B.The new wife was Cushite. This detail appears to be the primary factor as it was twice repeated. Consider that during the Egyptian New Kingdom (16th century B.C. onward), Egypt had conquered and was ruling over Kush (governed by an Egyptian Viceroy). As a subservient minority (and possibility even a co-captive), she would have departed on the Exodus with the Israelites. Certainly she would have felt more affinity for this enslaved people than the conqueror and master of her own people. The Bible is clear that other peoples departed with the Israelites:
The issue, for Miriam and Aaron would have been that she was associated with the Egyptians or, most probably, that she was other than an Israelite. Miriam and Aaron may not have liked that Moses was initially married to a Midianite but they would have understood the extenuating circumstances that led to that union. Now, here goes Moses marrying outside of the Israelites again! For the record, the Law only banned Israelites from taking wives of "those who live in the land," namely the peoples/nations who were under God's judgment in the land of Canaan (Exodus 34:15-16; cf. Genesis 15:16). Moses would have done no wrong in taking a subsequent wife who was a Cushite.
Occam's razor (commonly described as 'the simplest answer is most often correct') leads me to believe that solution 3 and sub-solution B are the correct answer as they minimize the number of "what ifs" that are necessary to arrive at the other possibilities. Certainly, it is completely unwarranted to make any absolute claim that Moses is an example of an Old Testament polygamist marriage.
Josephus' full account of Moses and Tharbis:
Article by Brent