21 And the Lord said to Moses, “When you go back to Egypt, see that you do before Pharaoh all the miracles that I have put in your power. But I will harden his heart, so that he will not let the people go. 22-23 Then you shall say to Pharaoh, ‘Thus says the Lord, Israel is my firstborn son, and I say to you, “Let my son go that he may serve me.” If you refuse to let him go, behold, I will kill your firstborn son.’”

24-26 At a lodging place on the way the Lord met him and sought to put him to death. Then Zipporah took a flint and cut off her son's foreskin and touched Moses' feet with it and said, “Surely you are a bridegroom of blood to me!” So he let him alone. It was then that she said, “A bridegroom of blood”, because of the circumcision.

27-31 The Lord said to Aaron, “Go into the wilderness to meet Moses.” So he went and met him at the mountain of God and kissed him. And Moses told Aaron all the words of the Lord with which he had sent him to speak, and all the signs that he had commanded him to do. Then Moses and Aaron went and gathered together all the elders of the people of Israel. Aaron spoke all the words that the Lord had spoken to Moses and did the signs in the sight of the people. And the people believed; and when they heard that the Lord had visited the people of Israel and that he had seen their affliction, they bowed their heads and worshipped. Exodus 4:21-31 English Standard Version.

While vs 27-31 are straight forward and tell of the happy reunion of Moses with his brother Aaron, and the hope that was stirred up in the hearts of the elders of Israel when they heard that God had seen their affliction, vs 21-26 probably raise a few questions. Does God harden hearts? Why was Moses' life in danger if God was sending him to rescue Israel out of Egypt?

Regarding the question of ‘hardening Pharaoh's heart’ I will simply share what the apostle Paul wrote. Speaking of decisions God makes, Paul said: “What shall we say then? Is there injustice on God's part? By no means! For He says to Moses, 'I will have mercy on whom I have mercy, and I will have compassion on whom I have compassion.' So then it depends not on human will or exertion, but on God, who has mercy. For the Scripture says to Pharaoh, 'For this very purpose I have raised you up, that I might show my power in you, and that my name might be proclaimed in all the earth.' So then God has mercy on whomever He wills, and He hardens whomever He wills.” Romans 9:14-18.

Paul anticipated our indignant response, and says: “You will say to me then, 'Why does He still find fault? For who can resist His will?' But who are you, O man, to answer back to God? Will what is moulded say to its moulder, 'Why have you made me like this?”'Has the potter no right over the clay, to make out of the same lump one vessel for honourable use and another for dishonourable use?” Romans 9:19-21. I hope to touch on this further as we go through Exodus.

We aren't told how they knew at the lodging place that Moses' life (or that of one of his sons) was in desperate danger. I can only assume that, in the course of their marriage, Moses told Zipporah of the words God had spoken to Abraham hundreds of years earlier. In Genesis 17:9-14 we read: “God said to Abraham, 'As for you, you shall keep my covenant, you and your offspring after you throughout their generations. This is my covenant, which you shall keep, between me and you and your offspring after you: Every male among you shall be circumcised. You shall be circumcised in the flesh of your foreskins, and it shall be a sign of the covenant between me and you . . . every male throughout your generations . . . shall surely be circumcised. Any uncircumcised male who is not circumcised in the flesh of his foreskin shall be cut off from his people; he has broken my covenant.'”

One lesson here is that, no matter how holy and important a role someone might have in God's service, it still requires absolute obedience. There may be an underlying lesson too. The Bible says: “Under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins.” (Hebrews 9:22) And in the Bible too, Christ is referred to as the 'bridegroom', and the Church is likened to His bride. He is the bridegroom who shed His blood for the bride.