Nisan

The Omer offering is brought on the sixteenth of Nisan, the second day of Passover. An omer of barley - the first of the harvest - is brought as a wave offering in the Temple, and from this moment, the new grain becomes permitted. From the day of the Omer, we begin to count the days until the festival of Shavuot, seven full weeks - the counting of the Omer. This counting connects the barley harvest of Nisan with the wheat harvest of Sivan, and the giving of the Torah. The Omer offering is the first act of dedication in the new harvest year. Before eating any of the new grain, the first of the harvest is brought to the Temple, and only afterward is the harvest permitted.