"And you shall count for yourselves from the day following the [first day of Passover]"—Leviticus 23:15.
We are commanded to count the omer. Each individual is commanded to count 49 days [from the day when the Omer Offering was brought in the Temple, on the second day of Passover], counting both the days and weeks that have elapsed.
Women are exempt from this mitzvah.
