I realize OT circumcision was of course only required of men. And, scripture does indicate it was commanded as man's responsibility for entering into covenant with God:
"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." Gen 17:14
But who circumcises the men children? At 8 days, they are too young to circumcise themselves, so it has to be their parents.
Genesis 17:10-12
This is my covenant, which ye shall keep, between me and you and thy seed after thee; Every man child among you shall be circumcised. 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.
So even though it was the males who were circumcised, it was the community's ("me and you and thy seed after thee") responsibility to ensure the (baby) males were circumcised. (See how the community gathered for the circumcision of John the Baptist).
Luke 1:58-59 And her neighbours and her cousins heard how the Lord had shewed great mercy upon her; and they rejoiced with her. And it came to pass, that on the eighth day they came to circumcise the child; and they called him Zacharias, after the name of his father.
Remember also that Abraham was credited with righteousness before he was circumcised. So although I agree that uncircumcised males were breaking the covenant, what is most important to God is faith. If an uncircumcised male had faith in God, it would only be a matter of time before he got circumcised (i.e. when he came to an age of understanding, he would act in obedience), despite his parents' lack of faith in not circumcising him. But time and again, it was the (physically) circumcised men who broke God's covenant (but not by uncircumcision), irrespective of the token of their covenant, due to lack of faith.
Also, I find your comments interesting. First, Moses' lack of faith. Is it possible that this event is recorded as further evidence that indwelling faith will indeed be recognized by one's actions or lack thereof? If so, the two, faith and action are tied together.
I think this event gives a number of lessons. First, that even "great" men can have lack of faith (which results in disobedience). Second, that the weaker and obscure (e.g. Zipporah) can have the faith that "great" men lack (evidenced by obedience). Third, that God is merciful in His judgements - so even though the son was in breach of the covenant, this was through no fault of his own, and God held Moses accountable, not the helpless child. Fourth, that God means what he says (Zipporah knew she had to circumcise, even if she didn't like the blood, or Moses would die).
I also think it shows the circumcision covenant wasn't just for males - it was for the community, and a female household head (e.g. a widow) might have just as much responsibility to ensure her males were circumcised as anyone else.
For this particular occassion, one of the extra biblical books indicates Moses made some strange agreement with Jethro (his father-in-law) about not circumcising his first-born (so he could marry Zipporah). While this book is not scripture, it would explain why Zipporah only needed to circumcise one son, why circumcision seemed to wait until after the eighth day (only when they left Jethro) and why Zipporah didn't hesitate to circumcise, but was upset with Moses (because he didn't do it).
"Yea, a man may say, Thou hast faith, and I have works: shew me thy faith without thy works, and I will shew thee my faith by my works.
Thou believest that there is one God; thou doest well: the devils also believe, and tremble.
But wilt thou know, O vain man, that faith without works is dead?" James 2:18-20
I think the passage is a good example of this. Zipporah showed faith that Moses lacked.
Secondly, God's intention to actually kill Moses points to the critical importance of his son's need for circumcision. According to scripture, without circumcision, Moses' son would definitely have been excluded from being in covenant with God.
I agree, but I also believe God is merciful (remember Abraham, saved while still uncircumcised). And if an uncircumcised man with faith in God came to an understanding of God's requirements, he would quickly get circumcised (remember, Abraham was circumcised on the same day God commanded it). It was the faith that was important to God, the excess skin circumcised was just a reminder or token of this faith.