”At a lodging place on the way, the Lord met Moses and was about to kill him. But Zipporah took a flint knife, cut off her son’s foreskin and touched Moses’ feet with it. ‘Surely you are a bridegroom of blood to me,’ she said. So the Lord let him alone. (At that time she said ‘bridegroom of blood,’ referring to circumcision.)”
Exodus 4:24-26 (NIV)

I remember the day when I was starting out in my faith and I read this verse. I was taken aback...what?! The Lord was going to kill Moses - after the burning bush experience, and after He had expressed support to Moses for the mission He had called Moses to! God was the one who had sought out Moses, introducing Himself and telling him of who Moses truly was and the purpose He had set apart for him. Why, then, did God seek to kill Moses? And what is happening with his wife?

To make sense of this, we have to take a closer look at circumcision and what it represents. One of the earliest covenants that God made, with Abraham and his descendants, is found in Genesis.

“This is My covenant which you shall keep, between Me and you and your descendants after you: Every male child among you shall be circumcised; and you shall be circumcised in the flesh of your foreskins, and it shall be a sign of the covenant between Me and you. He who is eight days old among you shall be circumcised, every male child in your generations, he who is born in your house or bought with money from any foreigner who is not your descendant. He who is born in your house and he who is bought with your money must be circumcised, and My covenant shall be in your flesh for an everlasting covenant. And the uncircumcised male child, who is not circumcised in the flesh of his foreskin, that person shall be cut off from his people; he has broken My covenant.”
Genesis 17:10-14 (NKJV)

As a seal or a sign of a covenant, God chose that the males would go through circumcision. In circumcision, God was giving the message to His people that I have cut you off for myself, set you apart, and consecrated you to be the people through whom my promises will stand. In the same way, this process would cause bleeding, signifying this as a blood covenant which means a covenant of life, just as the life of the animal is in the blood (see Leviticus 17:11). Simultaneously, it also represented the cutting away of the corruption of fallen man, that, in being in covenant with God, what is defiled could not be a part of His promise. It was done on the 8th day - representing new beginnings, because both the 1st and the 8th day are the beginning of a 7-day week.

All this foreshadowed the coming of the Messiah. Through His blood being shed, we are consecrated to Him and sin no longer has a part in us. When we accept this, we are made new
and become a new creation. This is why the New Testament writers speak of the “circumcision of the heart”. (See Galatians 2; 5:3; 6:11-15 and Colossians 2:11-13)

Back to Moses. Verse 14 gives us a clear picture of what the Lord was doing.

“And the uncircumcised male child, who is not circumcised in the flesh of his foreskin, that person shall be cut off from his people; he has broken My covenant.”
Genesis 17:14 (NKJV)

Essentially, God was about to carry out judgment because Moses would have walked into this place of leadership in which he was to help write the laws of Israel while himself being a law breaker. It is believed that Moses became ill and was not able to carry out the circumcision, which is why Zipporah ends up doing it. An understanding of the exclamation ‘Surely you are a bridegroom of blood to me’ could be that Zipporah herself, not being a Jew, did not like the rite or maybe was adverse to blood and was indignant that she had to do so.

In the end, the lesson can be seen in this: whenever God has spoken and we avoid following His voice, there are consequences, because He knows best. When we do not listen and obey, consequences are often a real result. We must always posture ourselves to repentance; not remaining in a place of not recognizing what God is doing or allowing. As we repent and obey, we will see God’s purpose, mercy, and goodness as He walks out the following road with us.

For further study:
Nick Batzig - How Was Circumcision a Sign of the Covenant? R.C. Sproul - Circumcision and Law
The Pulpit Commentary
Matthew Henry’s Concise Commentary
Cambridge Bible for Schools and Colleges