Deuteronomy 16:10, 16
And you shall celebrate the Feast of Weeks to the LORD your God with a freewill offering that you give in proportion to how the LORD your God has blessed you, . . .

Exodus 23:16
You are also to observe the Feast of Harvest with the firstfruits of the produce from what you sow in the field. And observe the Feast of Ingathering at the end of the year, when you gather your produce from the field.

Exodus 34:22
And you are to celebrate the Feast of Weeks with the firstfruits of the wheat harvest, and the Feast of Ingathering at the turn of the year.

Leviticus 23:15, 16
From the day after the Sabbath, the day you brought the sheaf of the wave offering, you are to count seven full weeks. . . .

Numbers 28:26-30
On the day of firstfruits, when you present an offering of new grain to the LORD during the Feast of Weeks, you are to hold a sacred assembly; you are not to do any regular work. . . .

2 Chronicles 8:13
He observed the daily requirement for offerings according to the commandment of Moses for Sabbaths, New Moons, and the three annual appointed feasts--the Feast of Unleavened Bread, the Feast of Weeks, and the Feast of Tabernacles.

Acts 2:1
When the day of Pentecost came, the believers were all together in one place.

1 Corinthians 16:8
But I will stay in Ephesus until Pentecost,

Hebrews 2:1
We must pay closer attention, therefore, to what we have heard, so that we do not drift away.