Exodus 34:22

You shall observe and celebrate the Feast of Weeks (Harvest, First Fruits, or Pentecost), the first fruits of the wheat harvest, and the Feast of Ingathering (Booths or Tabernacles) at the year’s end.

Exodus 23:16

Also [you shall observe] the Feast of Harvest (Weeks, Pentecost, or First Fruits), acknowledging the first fruits of your labor, of what you sow in the field. And [third] the Feast of Ingathering (Booths or Tabernacles) at the end of the year when you gather in [the fruit of] your labors from the field.

Numbers 28:16-31

‘The Lord’s Passover shall be on the fourteenth day of the first month [of each year].

Numbers 29:12-39

‘Then on the fifteenth day of the seventh month you shall have a holy [summoned] assembly; you shall do no laborious work, and you shall observe a Feast [of Booths] to the Lord for seven days.

Deuteronomy 16:10-15

Then you shall celebrate the Feast of Weeks to the Lord your God with a tribute of a freewill offering from your hand, which you shall give [to Him] just as the Lord your God blesses you;

John 7:2

Now the Jewish Feast of Tabernacles (Booths) was approaching.

Acts 2:1

When the day of Pentecost had come, they were all together in one place,

Treasury of Scripture Knowledge

Summary

And thou shalt observe the feast of weeks, of the firstfruits of wheat harvest, and the feast of ingathering at the year's end.

Bible References

Feast of weeks

Exodus 23:16
Also [you shall observe] the Feast of Harvest (Weeks, Pentecost, or First Fruits), acknowledging the first fruits of your labor, of what you sow in the field. And [third] the Feast of Ingathering (Booths or Tabernacles) at the end of the year when you gather in [the fruit of] your labors from the field.
Numbers 28:16
‘The Lord’s Passover shall be on the fourteenth day of the first month [of each year].
Numbers 29:12
‘Then on the fifteenth day of the seventh month you shall have a holy [summoned] assembly; you shall do no laborious work, and you shall observe a Feast [of Booths] to the Lord for seven days.
Deuteronomy 16:10
Then you shall celebrate the Feast of Weeks to the Lord your God with a tribute of a freewill offering from your hand, which you shall give [to Him] just as the Lord your God blesses you;
John 7:2
Now the Jewish Feast of Tabernacles (Booths) was approaching.
Acts 2:1
When the day of Pentecost had come, they were all together in one place,

General references

Exodus 23:14
“Three times a year you shall celebrate a feast [dedicated] to Me.
Leviticus 23:15
‘You shall count from the day after the Sabbath, from the day when you brought in the sheaf (tied bundle of grain) of the wave offering; there shall be seven complete Sabbaths (seven full weeks).
Deuteronomy 16:9
“You shall count seven weeks for yourself; you shall begin to count seven weeks from the time you first put the sickle to the standing grain.