This Sunday is the Day of Pentecost. The day where, in Act 2, the Holy Spirit “fell” upon the gathered ekklesia, with tongues of fire appearing over their heads.
Now the early believers normally met on Saturday evenings (as in Act 20:7-12), which marked the end of the Sabbath (“the first day of the week” according to the biblical calendar began Saturday evening at sundown, not Sunday morning as we have been trained to count). On this day they were meeting Sunday morning, because it was the Feast of Weeks, or Shavuot; pentecost (fifty) in Greek. In Lev 23:15-22, the ekklesia is charged with holding a holy convocation, or assembly, on that day, which is what the believers were doing. It was one of the seven annual feast days of the LORD, and one of the three high holy feast days, in which males were to appear before the LORD at the Temple in Jerusalem. It was also one of the three harvest feast days.
It was on this day, in history, that the Ten Commandments were given to Moses inscribed on tablets of stone with the finger of God. The rabbis tell in their tradition that the seventy elders of Israel on this day spoke, by the power of the Holy Spirit, in the seventy tongues of the nations, as a prefiguring of all the nations that would one day worship and serve the LORD in spirit and in truth. The outpouring of the Holy Spirit on this day fulfills Jer 31:31-34:
“Behold, the days are coming, declares the LORD, when I will make a new covenant with the house of Israel and the house of Judah, not like the covenant that I made with their fathers on the day when I took them by the hand to bring them out of the land of Egypt, my covenant that they broke, though I was their husband, declares the LORD. But this is the covenant that I will make with the house of Israel after those days, declares the LORD: I will put my law within them, and I will write it on their hearts. And I will be their God, and they shall be my people. And no longer shall each one teach his neighbor and each his brother, saying, ‘Know the LORD,’ for they shall all know me, from the least of them to the greatest, declares the LORD. For I will forgive their iniquity, and I will remember their sin no more.”
Shavuot/ Pentecost is a memorial feast; it is the memorial of the day when, by the infilling of the Holy Spirit, God inscribed His Law not only on tablets of stone, but also on the tablets of our hearts. By giving the Law, the Torah, and giving the Spirit, on the same feast day, then linking the two together forever by the prophecy in Jeremiah, and in many other places in the Scriptures, the LORD teaches us that His Law is still, of course, to be obeyed. But the power of obedience is by the Spirit of God, not by the will power of our flesh (Zec 4:6). This is walking by the Spirit.
Shavuot, Pentecost, or Weeks, is a holiday of Sabbath rest. Only food may be prepared that will be eaten on that day. We assemble together with the believers on that day; we honor the LORD in worship; we enjoy a picnic feast with our family, and play together.