Answer: Moses’ wife, Zipporah, calls Moses a “bridegroom of blood” in Exodus 4:25. To understand the appellation and the circumstance leading up to Zipporah’s use of it, we will look back about 400 years:

Genesis ends with Joseph as the prime minister of Egypt who, by God’s providence, saved Egypt from the famine and welcomed all his father’s household to live in the land of Goshen.

Exodus begins, centuries later, with the Israelites having become a great nation. They were persecuted by a Pharaoh who did not care what Joseph may have done and was afraid that so many foreigners in the land presented a security risk (Exodus 1:8–11). He ordered that all the male Israelite babies be killed, but the infant Moses was saved by his mother and eventually adopted by Pharaoh’s daughter (Exodus 2:1–10). He grew up as Egyptian royalty but never forgot that he was an Israelite. One day he defended an Israelite slave but killed an Egyptian in the process. Pharaoh wanted Moses killed, so Moses fled the country (Exodus 2:11–17). He became a shepherd in the land of Midian.

Moses lived in Midian for 40 years and married and had children. We don’t know what he may have told his wife and her family about his past, but, by all indications, he planned to be a shepherd the rest of his life and simply put Egypt and the captive Israelites out of his mind.

Then God appeared to Moses in the burning bush and told him to go back to Egypt and lead the Israelites out of slavery. Moses objected but eventually resigned himself to the task (Exodus 3:1—4:17). We can imagine that this would represent a major disruption in his family life, and his wife may not have been happy about the new direction he was taking.

On Moses’ trip back to Egypt, God intercepted him and “was about to kill him” (Exodus 4:24). Moses’ wife, Zipporah, “took a flint knife, cut off her son’s foreskin and touched Moses’ feet with it” (verse 25). At that time, she said, “Surely you are a bridegroom of blood to me” (verse 25)—“‘bridegroom of blood’ referring to circumcision” (verse 26). After that, God relented (verse 26). In this way, Zipporah saved her husband’s life.

The “bridegroom of blood” incident sounds strange to most readers. Why would God send Moses on a mission and then try to kill him? Why did circumcising the son satisfy God? First, we must recognize that there is perhaps some anthropomorphic language here because, if God really tried to kill Moses, He would have succeeded. It appears that God opposed or threatened Moses in some way (perhaps by severe illness), and this was apparently because Moses had not circumcised his son. Circumcision was the sign of the covenant between God and the descendants of Abraham (Genesis 17:9–14). Any uncircumcised male must be “cut off from his people” (verse 14). This could mean banishment or even death.

Moses, as a shepherd in Midian, had apparently completely given up being an Israelite, as shown in the fact that he had not circumcised his son. Perhaps Moses assumed he was already “cut off” from his people, so why should he bother to maintain the sign of the covenant? For whatever reason, and possibly even because of his Gentile wife's objections, he had not circumcised his own son.

God did not press the issue until it was time for Moses to go back to Egypt and become the leader of God’s covenant people. Before he could assume leadership, Moses would have to get his own house in order. We are not told the backstory, but we assume there had been some discussion about circumcision between Moses and his wife because Zipporah knew exactly what to do. After circumcising her son, she touched Moses’ feet with the foreskin—which would make sense if Moses were extremely ill and near death and therefore unable to perform the circumcision himself. Touching his feet with the foreskin was the act that “healed” Moses because it was tangible evidence that the sinful situation had been corrected.

Zipporah’s exclamation, “You are a bridegroom of blood to me,” is a complaint or a lament. She had to do something to her young son that was very painful and also very bloody. It was something that no mother would necessarily want to do, and she expressed her frustration with the way things had developed. Perhaps she, even more so than Moses, had planned to live out her days on the plains of Midian as a shepherdess and mother. Instead, her family had been completely uprooted to go on a journey she never expected to take. Additionally, she found herself doing something that she objected to. She is angry at Moses about it and calls him “a bridegroom of blood.” In English it might be paraphrased as “a husband of horrors,” “a mate of misery” or “a groom of gore.” The sentiment is, “If I had not married you, I would not have had to do this awful thing to my son.”

Zipporah is hardly mentioned again after the “bridegroom of blood” incident. We do not know what her relationship with Moses was like or if she ever truly accepted his God. Likewise, Moses’ children are not mentioned after this, and it is clear that they did not rise to leadership in Israel. It is not even clear that Moses’ family lived with him during the time he led Israel. This was not God’s ideal, but God used Moses in spite of his family dynamic. In the New Testament, church leaders are supposed to have their own houses in order, including having faithful wives and children (1 Timothy 3:1–12; Titus 1:5–9).