Leviticus 23:16

Even unto the morrow after the seventh sabbath. — That is, the day after the seven complete weeks, or the fiftieth day. Hence its name, “Pentecost, or fiftieth-day” feast in the New Testament (Acts 2:1; Acts 20:16; 1 Corinthians 16:8), and “feast of weeks” in the Old Testament (Exodus 34:12; Deuteronomy 16:10; Deuteronomy 16:16; 2 Chronicles 8:13). The fiftieth day, according to the Jewish canons, may fall on the 5th, 6th, or 7th of Sivan, the third month of the year, i.e., from the new moon of May to the new moon of June.

Shall offer a new meat offering. — That is, of the first-fruits of the wheat-harvest in contradistinction to the omer first-fruits, which was of barley-harvest. Hence this festival is also called “the feast of harvest” (Exodus 23:16), because it concluded the harvest of the later grain.