When do we start counting the Omer? That seems like a fairly easy question to answer. Just look at your Jewish calendar and you can see that the counting begins at nightfall, after the second seder (or the first night of chol hamoed in Israel). For the Jews of Eretz Yisrael of the Second Temple period (516 BCE-70 CE), the first day of the Omer was an opportunity for farmers to physically bring the first sheaves of their harvests to the kohen in the Beit HaMikdash (Leviticus 23:10-11): 

Speak to the Israelite people and say to them: When you enter the land that I am giving to you and you reap its harvest, you shall bring the first sheaf of your harvest to the priest.  He shall elevate the sheaf before the Lord for acceptance on your behalf; the priest shall elevate it on the day after the sabbath.

Verse 15 describes when the counting of the seven weeks begins: 

And from the day on which you bring the sheaf of elevation offering—the day after the Sabbath—you shall count off seven weeks. They must be complete.

The question of how to interpret the words “the day after the Sabbath” caused a powerful rift between the Pharisees and the Sadducees. The Sadducees, along with other Israelite sects, interpreted this phrase literally: the day after the Sabbath. This meant that if Pesach started on a Tuesday, the harvesting, bringing the sheaf to the kohen, and the counting of the Omer, would start on the following Sunday, the day after the Sabbath. The Pharisees, however, interpreted it as the day after the holiday—hence the custom to begin counting the Omer from the second day of Pesach.   

Mishnah Menachot 10:3 describes how the rite of the harvest of the Omer was performed. On the day before Pesach, emissaries of the court would go to the fields and tie the unreaped barley into bunches, while it was still connected to the ground. Thus, it would be easier to reap after the holiday. 

How did they harvest the Omer? Emissaries of the court would emerge on the eve of the festival of Passover and fashion the stalks of barley into sheaves while the stalks were still attached to the ground, so that it would be convenient to reap them.

Now comes the drama! The residents of all the towns who lived near the fields, would gather there so that each step of the reaping would be demonstrated with great fanfare:

The residents of all the towns adjacent to the site of the harvest would assemble there, so that it would be harvested with great fanfare. Once it grew dark, the court emissary says to those assembled:

Did the sun set? They said, Yes.   

Did the sun set? They said, Yes. 

Shall I reap the sheaves with this sickle? They said, Yes.                  

Shall I reap the sheaves with this sickle? They said, Yes.  

In this basket? They said, Yes.                         

In this basket? They said, Yes

Shall I reap the sheaves with this sickle? They said, Yes.                  

Shall I reap the sheaves with this sickle? They said, Yes.

In this basket? They said, Yes.                        

In this basket? They said, Yes

On the Sabbath he says to them, 

On this Sabbath? They answered, Yes.      

On this Sabbath? They answered, Yes. 

Shall I reap? And they answer, Reap!

Shall I reap? And they answer, Reap!

He repeated every matter three times, and they answered, Yes, yes, yes.

You can almost imagine the Jewish farmers chanting louder and louder, especially when the court emissary repeated the question, On this Shabbat? He wants all to assert that “the day after the Sabbath” means the day after the holiday! This is the halakha.

You might have already asked yourself the mishna’s question: Why is each stage of the barley harvest publicized with these enthusiastic chants?

The mishna answers: 

It is due to the Boethusians, as they deny the validity of the Oral Law and would say:  There is no harvest of the Omer at the conclusion of the first Festival day of Passover unless it occurs at the conclusion of Shabbat. The publicity was to underscore that the sixteenth of Nisan was the proper time for the Omer harvest.

The editors of the mishna present a spirited debate between first through third century rabbis and the Boesthianians, a sect related to the Sadducees. The debate was intense, and the rabbis were at a distinct disadvantage. Most other Israelite sects agreed with the Boesthians that the day after the Sabbath was indeed to be taken literally. This simple read of the text was embraced by the Samaritans, the authors of the Dead Sea Scrolls and centuries later, the Karaites. The rabbinic position strayed from this general consensus. Hence the vehemence of the Sages, whose teaching was based upon tradition, and not solely upon the biblical text. 

Bavli Menachot 65a-b presents a long and engaged series of refutations of the heretical position. Of particular interest to us is the response associated with Rabbi Yohanan b. Zakkai, the legendary Jerusalem sage who left the holy city to reestablish Torah at Yavneh near the destruction of the Temple. Rabbi Yochanan engaged his rivals and did not mince his words:

Rabban Yoḥanan ben Zakkai dealt with the Boethusians. He said to them: Fools, where did you come up with this idea?  [“This” meaning the Boethusian claim that  the verse literally means the day after the Sabbath.] No one answered him, except one elder who was prattling at him.

A single Boethusian “elder” spoke up against Rabbi Yohanan’s taunt. While the Talmud takes this to mean that only one person could respond, perhaps we might read against the grain—no one else bothered to answer him! Even this Boethusian elder is described disparagingly as having “prattled” at Rabbi Yochanan ben Zakai. The actual response of the Boethusian elder, however is learned, measured, lucid, respectful, and even loving:

He [the Boethusian elder]  said: Moses, our teacher, was a lover of the Jewish people and he knew that Shavuot is only one day. Therefore, [Moses] arose and established it after the following Shabbat, so that Israel would enjoy themselves for two days. 

Rabbi Yohanan responded polemically to this literalist, arguing from  Scripture:

He recited this verse in response: “It is eleven days’ journey from Horeb to Kadesh Barnea by the way of Mount Seir” (Deuteronomy 1:2). And if Moses, our teacher, was a lover of Israel, why did he delay them in the wilderness forty years? 

Still polite, even deferential, the Boethusian elder responded:  

He said to him: My master, with this [alone] you dismiss me?

Rabbi Yohanan responds with theatrical anger: 

He said to him: Fool! And will our perfect Torah not be as worthy as your frivolous speech?

Rabbi Yohanan goes on to provide biblical support for his position, and the Talmud continues with a long exposition explaining and developing rabbinic responses. For our purposes, it is enough to say that the date when the Omer is first harvested was a hot button issue even in the later part of the Second Temple period. In fact, this calendrical dispute continues to this day in conversations with contemporary Samaritans and Karaites—though happily, with less polemical language.

The Sages were adamant that the Oral Torah supersedes literalist interpretations of the written Torah, and publicly and polemically demonstrated their position. For the majority of Jews, their position won out. The clarion call of Sefirat ha-Omer still speaks to us today, as we, the students of the Sages, seek to understand the depth of our oral tradition.

Happy counting to all!