Menachot 65/66 why did the counting of the omer needed to start with a fixed time?

Question

I was looking at all the arguments made (against the Boethians) in favor of counting the omer from 16th Nisan until Shavuot - Menachot 65/66.

Then I went looking at Leviticus 23 and Deuteronomy 16.

In Deuteronomium 16:9 it says to begin to number from the time the sickle is first put to the standing crop. But no day, time or date is given.

So Leviticus 23 needs to help to determine when we need to start to count.

It says we need to bring the omer of the first fruits of the harvest and wave it: ממחרת השבת And ביום we wave it we need to offer... and we shall eat neither bread, nor parched corn, nor fresh ears, until היום הזה. And we shall count unto us from: ממחרת השבת. That is: מיום that we brought the sheaf of the waving; its duration: שבע שבתות תמימת תהיינה.

עד ממחרת השבת השביעת we count חמשים יום.

The start and duration are clear, but how was it determined that the words ממחרת השבת had to be referring to the Pesach week? Why did ‘the time the sickle was first put to the standing crop’ needed to be a fixed time? As a farmer, we normally look at our harvest to see when the time is right to put a sickle to it. So why (please forgive me for my horrible Hebrew grammar) couldn’t it refer to the ממחרת השבת של הניף את העמר? - the morrow after the שבת, which is היום, one waves the omer. I.e. at the moment these actions take place you need to start to count. In such a case the court could determine each year when one had to harvest and when one needed to wave and start the count.

Answer 1

The rabbis held that the words ממחרת השבת ("the day after the Shabbat") referred to the day after the holiday, not the day after Saturday. The proof for this is (as given by Rabbi Yosi on Menachot 66a) is that if Shabbat refers to Saturday, you don't know which Saturday in the year it is. As I understand it, the question on this is essentially: why do we care if we don't know which Saturday in the year it is, if every individual can bring it on the day after Saturday on which he harvests?

Here are two possible ways to derive from the Torah that the count must be the same for everyone, and not different for each farmer:

1. We learn from תספר לך (singular) in Deuteronomy that the counting is done by a court, and from וספרתם לכם (plural) in Leviticus that the counting is done by every individual (Menachot 65b-66a). Presumably, the individual count and the communal count should coincide.

2. If the count were individual, then every individual would have to give the same sacrifice at the beginning and end of the count. It seems that the rabbis took it as obvious that this was not the case, because they used this fact to derive that Leviticus 2:14, which also speaks of this offering, is communal and not individual (Torat Kohanim on this verse). Maybe this is a דבר הלמד מעניינו (something learned from context), since the many animal sacrifices that accompany the bread offered at the end of the count (Leviticus 23:18-19) are far beyond any obligatory individual sacrifice, but in line with the holiday communal sacrifices.

Also, it's worth nothing that the Boethusians apparently also agreed that Shavu'ot had to be on the same date for everyone, since they once tried to fool the sages into making Shavu'ot fall on a Sunday, in accordance with their method (Tosefta Rosh Hashana 1:14, Rashi on Rosh Hashana 22b). If the day were determined by the individual who was counting, there would be no need to force the sages to celebrate on the same day. So it seems that it was agreed unanimously that the counting had to be the same for everyone, but the question was only which day to start.