Can you explain what you mean here? God sought to kill Moses because he had disobeyed the commandment to circumcise. However, Zipporah performed the circumcision, which was just as valid, as she saved Moses life with her act. The commandment focused on ensuring the males were circumcised, not on who was to wield the izmel.
The commandment to circumcise was to Abraham
and his seed. Can a female not be the seed of Abraham? If not, why was Timothy circumcised (Acts 16:3)? His mother was the seed of Abraham, not his father.
Genesis 17:9-11 And God said unto Abraham, Thou shalt keep my covenant therefore, thou, and thy seed after thee in their generations. 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.
I think a mother's circumcision work would only be invalid if she snipped off the wrong bit...
Seriously though, the circumcision commandment focuses on the male children getting circumcised, but doesn't mention who is to perform it. That Zipporah saved Moses' life with circumcision says to me it is totally valid. Circumcision wasn't some sort of patriarchal thing, it was for all of Abraham's seed, but the commandment was that only the males needed to be circumcised. This doesn't mean females were excluded from anything related to circumcising. Some state that females were regarded as already circumcised from birth, never having a foreskin requiring circumcision.
Isn't this making circumcision out to be patriarchal? Why would a boy have a stigma about being circumcised by his mom? I guess I can understand to a degree where circumcision is used by men as an elitist thing against women, but I don't believe that kind of thinking is common today.
Although extrabiblical, 2 Maccabees 6:10 also informs us that mothers did take responsibility for circumcising their boys.
"For there were two women brought, who had circumcised their children; whom when they had openly led round about the city, the babes handing at their breasts, they cast them down headlong from the wall."