Leviticus 23:1-22 NKJV
23 And the Lord spoke to Moses, saying, 2 “Speak to the children of Israel, and say to them: ‘The feasts of the Lord, which you shall proclaim to be holy convocations, these are My feasts.
3 ‘Six days shall work be done, but the seventh day is a Sabbath of solemn rest, a holy convocation. You shall do no work on it; it is the Sabbath of the Lord in all your dwellings.
4 ‘These are the feasts of the Lord, holy convocations which you shall proclaim at their appointed times. 5 On the fourteenth day of the first month at twilight is the Lord’s Passover. 6 And on the fifteenth day of the same month is the Feast of Unleavened Bread to the Lord; seven days you must eat unleavened bread. 7 On the first day you shall have a holy convocation; you shall do no customary work on it. 8 But you shall offer an offering made by fire to the Lord for seven days. The seventh day shall be a holy convocation; you shall do no customary work on it.’ ”
9 And the Lord spoke to Moses, saying, 10 “Speak to the children of Israel, and say to them: ‘When you come into the land which I give to you, and reap its harvest, then you shall bring a sheaf of the firstfruits of your harvest to the priest. 11 He shall wave the sheaf before the Lord, to be accepted on your behalf; on the day after the Sabbath the priest shall wave it. 12 And you shall offer on that day, when you wave the sheaf, a male lamb of the first year, without blemish, as a burnt offering to the Lord. 13 Its grain offering shall be two-tenths of an ephah of fine flour mixed with oil, an offering made by fire to the Lord, for a sweet aroma; and its drink offering shall be of wine, one-fourth of a hin. 14 You shall eat neither bread nor parched grain nor fresh grain until the same day that you have brought an offering to your God; it shall be a statute forever throughout your generations in all your dwellings.
15 ‘And you shall count for yourselves from the day after the Sabbath, from the day that you brought the sheaf of the wave offering: seven Sabbaths shall be completed. 16 Count fifty days to the day after the seventh Sabbath; then you shall offer a new grain offering to the Lord. 17 You shall bring from your dwellings two wave loaves of two-tenths of an ephah. They shall be of fine flour; they shall be baked with leaven. They are the firstfruits to the Lord. 18 And you shall offer with the bread seven lambs of the first year, without blemish, one young bull, and two rams. They shall be as a burnt offering to the Lord, with their grain offering and their drink offerings, an offering made by fire for a sweet aroma to the Lord. 19 Then you shall sacrifice one kid of the goats as a sin offering, and two male lambs of the first year as a sacrifice of a peace offering. 20 The priest shall wave them with the bread of the firstfruits as a wave offering before the Lord, with the two lambs. They shall be holy to the Lord for the priest. 21 And you shall proclaim on the same day that it is a holy convocation to you. You shall do no customary work on it. It shall be a statute forever in all your dwellings throughout your generations.
22 ‘When you reap the harvest of your land, you shall not wholly reap the corners of your field when you reap, nor shall you gather any gleaning from your harvest. You shall leave them for the poor and for the stranger: I am the Lord your God.’ ”
The Israelites were not to eat any new grain, bread, or bushels until they had offered God the first fruits. They were brought to thank God for the produce of the soil, to call on Him for its prosperity, and to glorify Him by using it to help their neighbor. The first sheaves were offered as a wave offering the day after the Sabbath, that is, on a Sunday, and thereupon the full reaping or harvest began. In the year that Christ suffered His Passion, this fell right on that Easter Sunday when Christ rose from the dead. As St. Paul was inspired to write at 1 Corinthians 15:20, Christ, is the Firstfruits from the dead
Fifty days after the first sheaves had been offered as a wave offering, the Israelites were to offer God new fruits. Just as Christians do — they pray before and after the meal. Hence the feast was called the Feast of Pentecost (of the Fifty Days), or Feast of weeks, after the seven weeks, or the Feast of Firstfruits, after the new fruits. Valerius Herberger created a blessed prayer from all of this. Thus, Let us pray: O Lord Jesus, here I see that it was on this day that You poured out Your Holy Spirit upon Your apostles. For it is the proper work of the Holy Spirit (1) to explain the holy 10 Commandments to us rightly, that we may understand them better than the scribes and Pharisee; (2) to show us living consolation in Your most holy wounds when we have come to the knowledge of our sins by contemplation of the Ten Commandments; (3) to make us joyful before God, just as the Israelites made merry on the Feast of Pentecost, and to teach us to pray boldly, “Abba, dear Father” (Rom. 8:15); (4) to show us the full reaping and the rich, abundant harvest of Your precious merit, in which we have full abundance (Jn. 10:10); (5) to direct our heart to offer ourselves up to God as a voluntary gift, as St. Paul says: “Where the Spirit is, there is freedom” (2 For. 3:17). Send the Holy Spirit to me also and grant Him to perform such a blessed Pentecost labor in my heart also, that my heart may be a blessed Pentecost chapel acceptable to You. Amen (Great Works of God, M. Carver, Pt. VII, pg. 164 EP)