Here is an article taken from a Jewish website; JEWS, CHRISTIANS and THE WORD OF GOD.

Thought it might be of some interest to those Christians seeking a little more understanding of scripture.

Shavuot - Pentecost

Pentecost or Shavuot is the second of three pilgrim feasts, Passover and Sukkot being the other two. It occurs on the second day of Si'van (May or June) exactly fifty days after the Feast of Firstfruits. It means the Feast of "Weeks" because it commemorates the time when the Israelites stood at Mt. Sinai, seven weeks after they had fled Egypt. The last three days of this seven week journey was a time of purification. It would be here that the Israelites would receive the Ten Commandments. The Greek speaking Jews called this holiday "Pentecost"-the Feast of the Fiftieth Day. The holiday celebrates the first fruits of the full harvest, as well as the giving of Torah at Mount Sinai.

On this day, the Ten Commandments are read from Exodus and the story of Ruth is recounted . Ruth, a Moabitess, was married to Naomi's son. When Naomi's husband and sons died, Ruth was told to go home to her family. Her response was: "Entreat me not to leave thee, or to return from following after thee: for whither thou goest, I will go; and where thou lodgest, I will lodge: thy people shall be my people, and thy God my God:" (Ruth 1:16 KJV). Ruth was King David's great-grandmother.

Messianic Implications

Shavuot presents a tapestry of old and new, of things that were and things that were to come. The Messianic implications are enormous. The Book of Acts tells the story of Pentecost. Acts 2:1 tells us that: "When the day of Pentecost came, they were all together in one place." Did you ever wonder why they were together in one place? The answer is because they were there to celebrate Shavuot, one of the three pilgrim feasts which required each male to present himself in Jerusalem with an offering to the Lord!

One hundred twenty faithful followers gathered with the Messiah - ten from each of the twelve tribes of Israel who were commanded to "tarry in Jerusalem". Suddenly, The Ruach Ha Kodesh [Holy Spirit] filled the room. Tongues of fire came upon them just as Messiah had said in Acts 1:8. Legend has it that when God spoke to Moses at Sinai, He spoke in every language known to man. So, too, the disciples spoke every known language in the Upper Room. Power, however, is the true theme of Pentecost-- power to witness for Yeshua. "But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth." (Acts 1:8) The following comparison of Shavuot and Shavuot "fulfilled" adds clarity:

Shavuot and Shavuot Fulfilled

http://menorah.by.ru/english.htm