Pentecost or Feast of Firstfruits

(The next holy day following the Days of Unleavened Bread is the Feast of Firstfruits or the Feast of Sabbaths. The name Pentecost meant 'fiftieth' in the Greek speaking world.
It was called fiftieth because the high priest was to cut the first sheaf of grain on the weekly Sabbath during the days of unleavened bread. This ceremony pictured the first of the firstfruits; the first sheaf of the springtime harvest. It pictures the Risen Christ.)

Lev 23:15-16
"And ye shall count unto you from the morrow after the Sabbath, from the day that ye brought the sheaf of the wave offering, seven sabbaths shall be complete;
Even unto the morrow after the seventh sabbath shall ye number fifty days."

(Christ ascended to His Father on a Sunday, after being resurrected on late Sabbath afternoon. The wave sheaf pictures Christ.)

(The firstfruits pictures God's harvest from among mankind from the time of Christ till the Millennium and the Great White Throne Judgment.) Rev 20:1-5; 11-15

(There is Biblical proof that Paul not only kept God's annual Sabbaths, but taught Gentile converts to do so too.)

1 Cor.5:6-8
"Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump?
Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us:
Therefore let us keep the feast not with the old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth."

(Paul instructed the Gentile Christians in the Gentile city of Corinth to keep the Feast of Unleavened Bread!)

(Those who keep God's annual holy days know that Pentecost is the birthday of the church. When the Holy Spirit, with a loud, sound like a rushing wind filled the room where the apostles were assembled and they appeared to have flaming crowns of fire atop their heads.)

1 Cor 16:8
"But I will tarry at Ephesus until Pentecost."
(Paul wrote this nearly thirty years after Christ's resurrection.)