When I was reading in Numbers 12, it seems Moses took a second wife from Ethiopia late in his life. Is it true Moses had multiple wives?
In Numbers 12 we read this:
Num. 12:1 Then Miriam and Aaron spoke against Moses because of the Cushite woman whom he had married (for he had married a Cushite woman);
Num. 12:2 and they said, “Has the Lord indeed spoken only through Moses? Has He not spoken through us as well?” And the Lord heard it.
We read that Moses had taken a Cushite woman as a wife. Cush is the ancient name for the region called Ethiopia today. Moses's wife, Zipporah, was from Midian in Arabia. Midian and Cush are different places in the Bible, so this Cushite woman must be a different wife than the one Moses took while in Midian.
Nevertheless, nothing in the Bible suggests that Moses was married to these two women simultaneously. On the contrary, the evidence suggests Moses married the Cushite woman after Zipporah's death. The events of Numbers 12 occur when Moses is already over 80 years old, so it's very likely that Zipporah had died by that time. Since his first wife had died, Moses was able to marry again.
Further circumstantial evidence for Zipporah's death is found in the conflict between Miriam, Aaron and Moses. Moses' decision to (re)marry became Aaron's and Miriam's excuse to discredit Moses in an attempt to usurp his authority over Israel. The Bible consistently condemns taking multiple wives, and even Jesus Himself declared that when one man and one woman come together in marriage to become one flesh, and any additional marriage relationship is sin.
Yet in Numbers 12 we read God coming to Moses' defense, which strongly suggests that Moses had done nothing wrong in God's eyes by marrying the Cushite. These details support the conclusion that Moses married after Zipporah's death, though her death is not recorded in scripture.
Therefore, we must conclude that in Numbers 12 Moses was remarrying after having become a widower, not taking multiple wives.