Most commentators feel that what happened here was a life-threatening illness by which God was going to kill, to slay. It came to Moses, undoubtedly in his prayer or meditation, that the problem was that he was resisting God in the circumcision of his son. There is an interesting little sidelight here, because it seems from the information that is given that the reason the son had not been circumcised is that Moses conceded to Zipporah that the son would not be circumcised. What God was teaching Moses was that, as the head of the house, he was responsible to see that God's rules, God's orders, God's policies, God's direction was followed.
