Leviticus 23 challenges Israel to rehearse God's appointed times on an annual basis. The goal is that God would be revealed to the rest of the world by what He had done and that additionally the promised Messiah would be foreshadowed in the celebrations.
The Sabbath or Shabbat was the only WEEKLY convocation or rehearsal and reminded Israel and thus the world that God created for six days and rested the seventh, we should take a break once in awhile as well. The next seven festivals were to be celebrated annually and the first four were in the Spring. Passover/Pesach reminded Israel of the lambs blood that marked their door posts but it also foreshadowed the shed blood of Jesus Christ. The Feast of Unleavened Bread/HagHaMatzot was celebrated one day later and was a reminder of the flat bread that the Israelites carried with them as they left Egypt. It also pointed forward to the bread of life, Jesus Christ, whose body was broken in our place. First Fruits/Yom HaBikkurim was the third day of Passover. It was an opportunity for Israelites to bring to God the first part of their harvest in the Promised Land but it also promised that Jesus' resurrection form the dead would be the first of many. Those who trust in His atoning death cannot be held by the grave. Which brings us to the fourth festival, the last of the Spring Festivals.
Shavuot or Pentecost was a commemoration of God's giving the Torah to the people of Israel. Shavuot was to be celebrated 50 days after Passover, Pentecost means "fiftieth day". Passover marked Israel's release from Egypt. Pentecost or Shavuot, 7 weeks later, marked the receiving of the Torah and becoming a nation committed to serving God. Shavuot marked the end to the Passover season. Is it coincidence that seven weeks after the crucifixion of Jesus Christ, God the Father sends the Holy Spirit to indwell His own...on the day of Pentecost? Certainly not.
Four Spring festivals or sacred rehearsals, Passover - the blood, Unleavened Bread - sinless, First Fruits - resurrection, Pentecost - indwelling. Four rehearsals, four events in the ministry of Jesus Christ. Three fall festivals yet to look at, three events in the ministry of Jesus Christ yet to be fulfilled...stay tuned.