At a lodging place on the way YHWH met him and sought to put him to death.
#exodus 4:24 #shemot

The object of God's threat in Exodus 4:24 is ambiguous. Was YHWH threatening to kill Moses or his son? The text isn't precise. Since God had just threatened the firstborn son of Pharaoh, I suspect Moses' son is intended. In any case, God didn't actually want to kill anyone. Just as when he told Abraham to sacrifice Isaac, God's goal wasn't the death of a child, but a test of faith and a prophetic lesson for all of his people. One thing God might have been saying in this story: Don't tell the world to get their houses in order if yours isn't in order first.

Why hadn't Moses circumcised his son on the eighth day as God had instructed Abraham? Maybe he didn't know it was important. Maybe Zipporah objected and he was trying to keep the peace in his marriage. Torah doesn't explain. Whatever the reason, God clearly did not approve.