Shavuot -- The Feast of Weeks
In Leviticus 23:15 - 21, we are given the details of the feast of weeks, known as "Shavuot" in Hebrew. We are instructed to count 50 days from the day after Pesach / Passover and have a set-apart convocation on the the fiftieth day. This feast coincides with the giving of the Torah on Mt. Sinai to the Children of Israel and the mixed multitude that accompanied them out of Egypt. Centuries later, the Ruach Elohim was given to the congregation of believers at "Pentecost".(Acts 2)
We are instructed in Vayikra / Leviticus to bring leavened bread out of our homes to be a wave offering to YHVH. It is considered that this is symbolic of Judah and Israel, in that, even though permeated with leaven (which is symbolic of a sinful nature or evil inclination) we are dedicated for our Elohim.
So, if the giving of the Torah was the wedding of Am Segula (the Chosen People) to the Ruler of the universe, then the giving of the Ruach HaKodesh as a pledge of the faithfulness of His Covenant was the "renewal of vows". It is for this reason that B'nei Mitzvot and wedding vow renewal ceremonies are held on this day at our congregation. Not only is it in keeping with the theme of the feast, but it takes away the uniqueness of a single bar or bat mitzvah or single wedding vow renewal and places the emphasis on the collective. In other words, it wasn't just Moshe who accepted the commandments on Mt. Sinai, it was all of Israel, saying "We will do, then we will hear."
Shavuot also holds an important place as the end of the spring feasts, the conclusion of Passover, as it were. Just as Pesach / Passover marked our exodus out of Egypt (and for each of us personally, the Egypt of sin), the following seven weeks mark the getting the leaven out of our lives and the striving for spiritual growth. On the fiftieth day, fifty being the number of Jubilee, we arrive at Shavuot, the day that marks our dedication to our Creator / Redeemer / Bridegroom and Sovereign, and our spiritual marriage to Him. Shavuot is also the bridge to the fall feasts, Yom Teruah, Yom Kippur and Sukkot, gateways to eternity with our Creator and Sovereign. HalleluYah!