Christ was careful to explain what was "fulfilled" in Him and what remained still intact from His earlier dealings with mankind. He "fulfilled" and brought to an end the Law of Moses. It ended. It was fulfilled. But everything else remained and was still in effect. Part of His explanation was as follows:
3 And he said unto them: Marvel not that I said unto you that old things had passed away, and that all things had become new.
5 Behold, I am he that gave the law, and I am he who covenanted with my people Israel; therefore, the law in me is fulfilled, for I have come to fulfil the law; therefore it hath an end.
6 Behold, I do not destroy the prophets, for as many as have not been fulfilled in me, verily I say unto you, shall all be fulfilled.
7 And because I said unto you that old things have passed away, I do not destroy that which hath been spoken concerning things which are to come.
8 For behold, the covenant which I have made with my people is not all fulfilled; but the law which was given unto Moses hath an end in me. (3 Nephi, 15.)
Was Abraham a prophet? Did he live before Moses? Was the covenant with him fulfilled in Christ's fulfillment of the Law of Moses? If Abraham preceded Moses by more than three centuries, how is the later Law of Moses related to the earlier covenant?
Here is part of the covenant between Abraham and God, to endure throughout all generations of those who claim part of Abraham's covenant:
7 And I will establish my covenant between me and thee and thy seed after thee in their generations for an everlasting covenant, to be a God unto thee, and to thy seed after thee.
8 And I will give unto thee, and to thy seed after thee, the land wherein thou art a stranger, all the land of Canaan, for an everlasting possession; and I will be their God.
9 ¶And God said unto Abraham, Thou shalt keep my covenant therefore, thou, and thy seed after thee in their generations.
10 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.
11 And ye shall circumcise the flesh of your foreskin; and it shall be a token of the covenant betwixt me and you.
12 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.
13 He that is born in thy house, and he that is bought with thy money, must needs be circumcised: and my covenant shall be in your flesh for an everlasting covenant.
Since the covenants between God and man were established in the heavens before the foundations of the world, as Joseph explained, I suspect the covenant of circumcision did not originate with Abraham. I suspect it was restored through him, but came down from the beginning. I believe if we had a full record we would find that originally the covenant was established through Adam. That it was originally intended to be performed by the male in contemplation of marriage. That the covenant of marriage, like all covenants, required the shedding of blood to be in effect. For the man, circumcision sealed with the shedding of blood his covenant to marry. For the wife, the virgin sacrificed blood at the marriage. But those things are now long forgotten, lost to time, and could only be known today by revelation.
If Joseph's statement is correct, and Adam had the fullness of the Gospel, then every prophet from the beginning has only "restored" lost truth. It has been a search to return to the original truth. After all, Christ came to Adam three years previous to his death and comforted him. (D&C 107: 53-57.) Such an event strongly indicates Adam had the fullness. The Gospel is, therefore, in all likelihood a search into the ancient order of things, not a leap forward into something new. In order to go forward, we will need to go back.
It is an interesting question to contemplate whether the Lord was serious about the token becoming a memorial of His "covenant [which] shall be in your flesh for an everlasting covenant." Also, although the New Testament debates over "those of the circumcision" determined not to require circumcision of adult converts, they did not have 3 Nephi, Chapter 15 to inform their debate. (For New Testament references, see, e.g., Romans chapters 2 & 4, Galatians chapter 5, among many other places.)
I would doubt there will be any uncircumcised males included in the latter-day Zion. It is, at least for me, an interesting question to contemplate.
