And thou shalt say unto Pharaoh, Thus saith the Lord", Israel is my son, even my firstborn: And I say unto thee, Let my son go, that he may serve me: and if thou refuse to let him go, behold, I will slay thy son, even thy firstborn."
And it came to pass by the way in the inn, that the Lord met him, and sought to kill him. Then Zipporah took a sharp stone, and cut off the foreskin of her son, and cast it at his feet, and said, Surely a bloody husband art thou to me. So he let him go: then she said, A bloody husband thou art, because of the circumcision. Exodus 4:22-26 KJV
Some assert that God was going to kill Moses, and others his son. However, there does not appear to be adequate support for either. Some say that God would be justified in killing Moses because he failed to circumcise his son, but the bible is not clear on who is held responsible for failure to perform circumcision:
And ye shall circumcise the flesh of your foreskin; and it shall be a token of the covenant betwixt me and you. And he that is eight days old shall be circumcised among you, every man child in your generations, he that is born in the house, or bought with money of any stranger, which is not of thy seed. He that is born in thy house, and he that is bought with thy money, must needs be circumcised: and my covenant shall be in your flesh for an everlasting covenant. And the uncircumcised man child whose flesh of his foreskin is not circumcised, that soul shall be cut off from his people; he hath broken my covenant. Genesis 17:11-14 KJV
This is the beginning of circumcision, where God is speaking to adults - because eight-day-old infants cannot perform this on their own. If the child must be 8 days old then surely Moses' child could not be held responsible. If Moses were responsible then why would the child be cut off instead?
I believe that God is speaking about Pharaoh's firstborn. It seems that there should be a break between the verses, because it seems to jump into another situation. Many translations use 'him', or 'Moses'. But the KJV does not use names. If God were to kill Moses, surely he could have done it earlier. If Zipporah did not like the procedure that's all it was.
To this day I have not found a sensible answer to my Exodus 4 question. Verse 24 seems pivotal:
And it came to pass by the way in the inn, that the Lord met him, and sought to kill him.
Who was God going to kill, why was He going to kill them, and why did the circumcision prevent it?