Was the Day of Pentecost one of the seven feasts of the Lord in Leviticus 23?
Yes. The Day of Pentecost is one of the seven feasts of Jehovah listed in Leviticus 23. It fell 50 days after Passover, arising from the counting of seven complete sabbaths plus the next day, and it was practiced year in and year out throughout Israel's history.
Les explains that as chapter 2 opens with the Day of Pentecost, it must be connected back to Leviticus 23, where it is listed as one of the seven feasts of Jehovah. He notes the sequence: Passover, then Unleavened Bread in verse 6, then First Fruits in verses 9–14, and then the next feast in verse 15. From the morrow after the sabbath, Israel was to count seven sabbaths complete—49 days—and then go to the next day, making 50. The word Pentecost arises from that, so it was the fiftieth day after Passover. Les says it became a feast day and was one of the seven feasts practiced year in and year out throughout Israel's history.