What's all this about then?

Pretty much every year for the last few years I've resolved to read through the King James version of the Bible. Never quite managed it, but still find it an interesting and important exercise, personally and professionally.

I have a great One-Year Bible (ISBN 1-4143-0700-4) which is arranged with each day having a sequential chunk from the Old Testament, the New Testament, a Psalm and a Proverb.

This way, you are still progressing right through, but you're less likely to give up when you hit the great swathes of 'begats' in the Old Testaments, because you've still got narrative over the page in your New Testament extract.

Today, 2nd Jan, for example, it's:
OT Genesis 3:1-4:26
NT Matthew 2:13-36
Psalm 2 (obviously)
Proverb 1:7-9

However, I've been browsing ahead, and was struck (as in previous years) by one of the most curious and inexplicable passages in the whole Bible.

It's in Exodus 1. The verses are 24-26. I'll give you the verses leading up to it, and the verse after it, so you can see that there's no real context to why it suddenly pops up so bizarrely.

4:20 And Moses took his wife and his sons, and set them upon an ass, and he returned to the land of Egypt: and Moses took the rod of God in his hand.

4:21 And the LORD said unto Moses, When thou goest to return into Egypt, see that thou do all those wonders before Pharaoh, which I have put in thine hand: but I will harden his heart, that he shall not let the people go.

4:22 And thou shalt say unto Pharaoh, Thus saith the LORD, Israel is my son, even my firstborn:

4:23 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.

4:24 And it came to pass by the way in the inn, that the LORD met him, and sought to kill him.

4:25 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.

4:26 So he let him go: then she said, A bloody husband thou art, because of the circumcision.

4:27 And the LORD said to Aaron, Go into the wilderness to meet Moses. And he went, and met him in the mount of God, and kissed him.

4:28 And Moses told Aaron all the words of the LORD who had sent him, and all the signs which he had commanded him.

4:29 And Moses and Aaron went and gathered together all the elders of the children of Israel:

So why did the Lord decide to kill Moses? How did Moses' wife know that circumcising her son might divert the Lord's wrath? (Some versions say that she 'touched the foreskin to Moses's feet'.) What's all that about, then?

Here's a couple of scholarly interpretations, but your guess is as good as mine.