The Feast of Pentecost is a Biblical Holiday celebrating the time when Yahuwah led the children of Israel to the wilderness at Mt. Sinai to give them the Law. It was considered a Wedding Betrothal to Elohim as described in Yirmehyahu (Jeremiah) 2:2. A Jewish Betrothal is similar to both a marriage and a marriage engagement. It is similar to a marriage in that they are legally binding and the two become man and wife at that time. It is similar to a marriage engagement in that the two do not live together yet and are waiting in eager anticipation for that great day when they will be together.
In a Biblical Jewish Betrothal, there is a written contract called a ketubah that stipulates the requirements of the Bride and Groom. The Bible is the betrothal contract between Elohim and His Bride in the Old Covenant. As was customary in Jewish weddings, there was a person known as the "Friend of the Groom". It was his job to escort the Bride to the Groom for her Betrothal. Moses was the Friend of the Groom and escorted Israel to the wilderness for her betrothal to Elohim in the Old Covenant. This event had major significance to Yahuwah's Plan of Redemption for Mankind. That is why Yahuwah commanded it to be celebrated forever as a memorial Holiday. The Bible calls it "Elohim's appointed time". When this Holiday was first set up it pointed to the time when Yahuwah would write the betrothal contract on the hearts and minds of men rather than on stone tablets. That's why Yahuwah's instructions on when to celebrate it is so important. It was on this very day, years later, that the Holy Spirit was first poured out on believers of Yeshua proving that He was the Messiah.
Today it is celebrated as an anniversary of that special day when the Holy Spirit was first poured out on believers, placing the Betrothal contract on their minds and hearts. You can read about this special event in Acts chapter 2. John the Baptist was considered a friend of the Groom for the New Covenant Betrothal as He lead people to repentance and their Jewish Groom Yeshua. After Yeshua died on the cross during Passover paying the bride price for His bride, and after He was buried, and after He rose from the dead, the Holy Spirit was poured out on the Biblical Holiday of Pentecost. All of the early harvest Holidays were fulfilled by Yeshua at these appointed times. The Jews were even expecting the Messiah to come at this time from other prophesies in Scripture. Unfortunately they were looking for the Conquering King and not the Suffering Servant that was also prophesied in their Scripture.
Now that Yeshua, the Suffering Servant, has completed His appointed times, Yeshua the Conquering King will be coming in the not too distant future. He is one and the same and Salvation for all who will receive Him in marriage. Have you said yes to His invitation of Betrothal?