According to the Old Testament ceremonial laws, the feast of Pentecost came exactly seven weeks after the Passover celebration—on the fiftieth day after the Passover, hence the name Pentecost meaning fiftieth. For the Jews, Pentecost recalled the giving of the Law on Mount Sinai marking the institution of God’s Old Testament Church. Pentecost also served as a Jewish thanksgiving festival for the harvest; the day the people offered to the LORD two loaves of bread made from the first fruits of wheat.
For us, Pentecost—also known as Whitsunday (derived from the white garments worn by those baptized on this day)—marks the beginning of God’s New Testament Church. This festival serves as one of thanksgiving for firstfruits as well, not merely the firstfruits of an earthly harvest, but of a harvest of souls as the Holy Spirit works through God’s word and baptism to bring souls into the kingdom of God.