As I explained in my book Mysteries of Judaism 1, the ancient religious Jewish group Pharisees, who existed from about 320 BCE until 70 CE, and the rabbis who followed them changed all of the Jewish practices and holidays in some ways. Let’s look at the laws of counting the omer, called in Hebrew Sefirat Ha’Omer, and the holiday of Shavuot.
Leviticus 23 speaks about the holidays of Passover on the fourteenth day of the first month and the seven day holiday of The Feast of Unleavened Bread that begins on the fifteenth day. In 23:15 and 23:16 the Torah states: “You should count from the day after the Sabbath, from the day that you brought the Omer that is waived [a weight of barley grain]; seven weeks; they should be complete; until the day after the seventh Sabbath, you should count fifty days” [when a new offering is brought in the temple of the newly harvested wheat grain]. The fiftieth day is called Shavuot, or “weeks,” because it concludes the seven “weeks” from “the Sabbath” in Exodus 34:22 and Deuteronomy 16:10, and Feast of Harvest in Exodus 23:16 and Day of First fruits in Numbers 28:26.
The plain sense of the words of this command (words I italicized) is that the Israelites should observe the celebration of the wheat harvest on the fiftieth day after the Sabbath following the holiday of Passover. The time begins on a Sunday (“the day after the Sabbath”) and Shavuot is to be observed on a Sunday the fiftieth day that follows.
In essence, the holiday has no significance in the Bible other than a harvest festival. The word “Sabbath,” used twice in the command is the seventh day; “they shall be complete [weeks]” is seven days from Sunday through Saturday; and the command to count does not require a verbal counting, just as a verbal counting is not required when the Torah states that a menstruate “must count seven clean [bloodless] days” before becoming clean (Leviticus 15:28) and the Israelites didn’t have to physically “count seven cycles of Sabbatical years” until the Jubilee year (Leviticus 25:8).
It is no surprise that the Bible was unable to set a date when Shavuot, the Feast of Harvest, would occur since the date of the Sunday when the count began varied from year to year. It is also no surprise that the harvest festival is called Shavuot, meaning “weeks,” because it occurs after seven complete weeks of seven days. However, the Pharisees and rabbis gave a new meaning to the biblical words so that we would know when Shavuot occurs.
They interpreted the word “Sabbath” to mean the holiday of The Feast of Unleavened Bread, developed the idea to count 49 days, not 7 weeks, created a law requiring all Jews to ceremoniously count each day between Passover and Shavuot with a blessing and called it the counting of the Omer, thereby setting the sixth day of the month Sivan as the date of Shavuot, a date not possible according to the biblical procedure, and they gave Shavuot a non-biblical meaning. Shavuot became the day the Torah was given to the Israelites at Sinai, even though the Torah only states that the Decalogue (the Ten Commandments) were given at Sinai and much of the content of the Torah tells of events that occurred after the Israelites left Sinai.
None of this should stop us from counting the Omer or enjoying the holiday of Shavuot or in any way minimizing our study of the Torah.