Exodus 22:29

29“You shall not delay to offer from the fullness of your harvest and from the outflow of your presses. ^aThe firstborn of your sons you shall give to me.

Exodus 34:22

22 ^bYou shall observe the Feast of Weeks, the firstfruits of wheat harvest, and the Feast of Ingathering at the year’s end.

Leviticus 23:9-21

The Feast of Firstfruits

9And the Lord spoke to Moses, saying, 10“Speak to the people of Israel and say to them, ^cWhen you come into the land that I give you and reap its harvest, you shall bring the sheaf of ^dthe firstfruits of your harvest to the priest, 11and he shall ^ewave the sheaf before the Lord, so that you may be accepted. On the day after the Sabbath the priest shall wave it. 12And on the day when you ^fwave the sheaf, you shall offer a ^gmale lamb a year old without blemish as a burnt offering to the Lord. 13 ^hAnd the grain offering with it shall be two tenths of an ephah ▼

▼An  ephah was about 3/5 bushel or 22 liters

of fine flour mixed with oil, a food offering to the Lord with a pleasing aroma, ^jand the drink offering with it shall be of wine, a fourth of a hin. ▼

▼A  hin was about 4 quarts or 3.5 liters

14And you shall eat neither bread nor grain ^lparched or ^mfresh until this same day, until you have brought the offering of your God: it is a statute forever throughout your generations in all your dwellings.

The Feast of Weeks

15 ⁿ“You shall count seven full weeks from the day after the Sabbath, from the day that you brought the sheaf of the ^owave offering. 16You shall count ^pfifty days to the day after the seventh Sabbath. Then you shall present a grain offering of ^qnew grain to the Lord. 17You shall bring from your dwelling places two loaves of bread to be waved, made of two tenths of an ephah. They shall be of fine flour, and they shall be baked with leaven, as ^rfirstfruits to the Lord. 18And you shall present with the bread seven lambs a year old without blemish, and one bull from the herd and two rams. They shall be a burnt offering to the Lord, with their grain offering and their drink offerings, a food offering with a pleasing aroma to the Lord. 19And you shall offer one ^smale goat for a sin offering, and two male lambs a year old as a sacrifice of ^tpeace offerings. 20And the priest shall ^uwave them with the bread of the firstfruits as a wave offering before the Lord, with the two lambs. ^vThey shall be holy to the Lord for the priest. 21And you shall make a proclamation on the same day. You shall hold a holy convocation. You shall not do any ordinary work. It is a statute forever in all your dwelling places throughout your generations.

Numbers 28:26-31

Offerings for the Feast of Weeks

26“On ^wthe day of the firstfruits, when you offer a grain offering of new grain to the Lord at your Feast of Weeks, you shall have a holy convocation. You shall not do any ordinary work, 27but offer a burnt offering, with a pleasing aroma to the Lord: ^xtwo bulls from the herd, one ram, seven male lambs a year old; 28also their grain offering of fine flour mixed with oil, three tenths of an ephah for each bull, two tenths for one ram, 29a tenth for each of the seven lambs; 30with ^yone male goat, to make atonement for you. 31Besides the regular burnt offering and its grain offering, you shall offer them and their drink offering. ^zSee that they are without blemish.

Deuteronomy 16:9-12

The Feast of Weeks

9 ^aa“You shall count seven weeks. Begin to count the seven weeks from the time the sickle is first put to the standing grain. 10Then you shall keep ^abthe Feast of Weeks to the Lord your God with ^acthe tribute of a freewill offering from your hand, which you shall give ^adas the Lord your God blesses you. 11And ^aeyou shall rejoice before the Lord your God, you and your son and your daughter, your male servant and your female servant, the Levite who is within your towns, the sojourner, the fatherless, and the widow who are among you, at the place that the Lord your God will choose, to make his name dwell there. 12 ^afYou shall remember that you were a slave in Egypt; and you shall be careful to observe these statutes.

Acts 2:1

The Coming of the Holy Spirit

1When ^agthe day of Pentecost arrived, they were all together in one place.