Thousands of years ago, Israelite people would bring a measure of their spring barley harvest to the Temple in Jerusalem in the spring as an offering of gratitude for a successful harvest. After that, they would count forty-nine days to the next harvest, the wheat, which was essential to survival over the following months. This practice was then codified and described in the Bible.
Since those ancient times, Jewish evening prayers throughout the world follow a set pattern, adding two sentences for seven weeks each spring, starting on the evening of the second Passover Seder and continuing for the next forty-nine days. This is the "Counting of the Omer," and with the guidance of Rabbi Min Kantrowitz this counting is full of spiritual insight.