In my reading of the New Testament and the Book of Mormon, I'm struck by the veiled nature of the references to the words spoken by Jesus when he institutes the sacrament of the Lord's Supper. It seems that none of the writers want to record the actual prayer, but instead record Christ's explanation of the prayer, until we get to Moroni, who records the entire thing verbatim. Why is this?
First of all, my contention that the actual prayers aren't recorded needs some support. In Matthew we read:
And as they were eating, Jesus took bread, and blessed it, and brake it, and gave it to the disciples, and said, Take, eat; this is my body. And he took the cup, and gave thanks, and gave it to them, saying, Drink ye all of it; for this is my blood of the new testament, which is shed for many for the remission of sins.Notice he "blessed it" and "gave thanks," but the words recorded are his instructions to the Apostles after he did that, not the actual words used in the blessing or the giving thanks. The event is recorded in Mark nearly identically, and also in Luke. John does not record the event at all, which I'll return to later.
When Jesus visits the Nephites, he also institutes this sacrament. Not only do we also not get a record of the words used to bless the emblems, we get a fuller explanation of the ordinance, and this explanation closely parallels the words of the prayers we receive later from Moroni (and that we use today), so much so that a reader might not realize at first that, once again, the scriptural scribe has not recorded the prayer itself.
So it seems as if the words used to bless the sacramental emblems are not to be recorded, until we get to Moroni, where he writes them completely. What's up with that?
I believe Moroni "ended" the Book of Mormon three times. The first time he finished the work of his father soon after the final battle at Cumorah. In Morm. 8:1 he tells us he has "but few things to write, which things I have been commanded by my father." In Verse 5 he writes that he has little room left and he has no ore to make more plates. This doesn't line up with the fact that he wrote the sealed portion of the plates (see Ether 4:4-5), which represent something like half to two-thirds of the total volume. Clearly he finishes the little Book of Mormon (meaning Morm. 8 and 9) in very different circumstances than he faces while writing the Book of Ether. In Ether 13, Moroni tells us he will "finish my record," and he starts Moro. 1:1 by telling us, "I had supposed not to have written more." What types of things does he write in the Book of Moroni?
It's a grab-bag of every remaining bit of information he can remember. He's the last person around who knew how the believers operated and he knows that anything he doesn't record will die with him. The first six chapters are short because he's following the "oh, yeah, I should write that down, too" method of writing. Then he copies a sermon and two letters from his father. The only original bit of the Book of Moroni is when he tries, for the third time, to bring the record to a close.
I believe that Moroni would have never written the sacramental prayer if he wasn't convinced that it would be otherwise lost. When Matthew, Mark, Luke, and Mormon all had an opportunity to write it down, they intentionally demurred. They explained the prayers, but they didn't record them. This seems to indicate that the words of the sacramental prayers were seen as too sacred for recording like everything else.
And this helps explain John's complete failure to mention the ordinance at all in two ways. First, if John felt the prayers were too sacred to record, he wouldn't have written them down unless he thought he had to. Second, John knew he wasn't going anywhere, so he didn't have to write them down.