The Day of Pentecost (2:1)
The day called “Pentecost” is named after the Greek word pentekostos, which means “fiftieth.” It was the only Old Testament festival determined by counting. On the day after the Sabbath after Passover, the ancient Israelites selected a sheaf of the first grain that had been harvested in the spring. This grain became an offering, and the priest waved it “before the Lord” (Leviticus 23:11-12). Pentecost was observed in ancient Israel on the 50th day after this (verse 15).