Shavuot (Pentecost)

From the day of the waved sheaf, seven complete weeks are counted, and the fiftieth day is Shavuot — the only feast whose date is reached by counting. Tradition links it to the giving of the Torah at Sinai, where God's voice spoke out of fire (Exodus 19-20).

Acts 2 happens exactly on this feast: "when the day of Pentecost came" (the Greek name of Shavuot, "fiftieth"), the Spirit descended with a sound from heaven and tongues like fire. At Sinai the Torah was written on tablets of stone; at the Shavuot of Acts 2, according to Jeremiah 31:33, it began to be written on hearts.

It is also the feast of the two leavened loaves waved together — and the day when about three thousand were added (Acts 2:41), the inverse echo of the three thousand who fell at the golden calf (Exodus 32:28).