The three Spring Feasts all fall within a few days of each other. The fourth Feast, Shavuot or Pentecost occurs 50 days after the Wave Offering on Firstfruits; it is almost two months later but yet is connected to the Spring Feasts by The Counting of the Omer. Starting on Firstfruits, each day is counted and remembered, up to the 50th day – Shavuot. This day is also a Firstfruits offering for the 2nd harvest, the wheat harvest. It is tradition to read the Book of Ruth during this time because it takes place during the barley and the wheat harvests.
It was also 50 days after Israel’s Red Sea Crossing (when they became God’s Firstfruits Offering) until Moses met God on Mt Sinai to receive Torah. And on Shavuot 1,500 years later, God poured out His Spirit upon the Believers in the Upper Room in Jerusalem. Torah written on cold stone tablets at Mt Sinai; Torah written on men’s hearts and minds in the Upper Room in Jerusalem!