Shemini Atzeret (Convocation of the Eighth Day, Lev. 23:33–36, 39–43), the day following the seven days of Sukkot (Feast of Tabernacles or Booths), and Shavuot (Pentecost) are “buddies.” The symbolism of one is mirrored in the other. What happened on Shavuot throughout the Bible is a “shadow,” a likeness, of what will happen on a Shemini Atzeret during the Day of the LORD.
There are conjunctions in Israel’s history between the days of Sukkot (Feast of Tabernacles or Booths) and key events, from the Flood to the time of David and Solomon to Yeshua (Jesus) mission on Earth to the coming Day of the LORD. Rather than coincidences, these intersections teach us about God and His Messiah.
God will put a trial on the nations who do not come to the Great Ingathering, i.e., the Feast of Sukkot (Tabernacles). God told Israel to bring in their laborers to Sukkot — even the “stranger,” or foreigner. So this among God’s appointments with mankind is not just for the House of Yehudah (Judah) or the House of Israel. God wants to “harvest” the peoples of the world into a new reality without sin and death.