Deuteronomy 16:9

7You shall roast and eat it in the place which the LORD your God chooses. In the morning you shall return to your tents.

8Six days you shall eat unleavened bread. On the seventh day shall be a solemn assembly to the LORD your God. You shall do no work.

9You shall count for yourselves seven weeks. From the time you begin to put the sickle to the standing grain you shall begin to count seven weeks.

10You shall keep the feast of weeks to the LORD your God with a tribute of a free will offering of your hand, which you shall give according to how the LORD your God blesses you.

11You shall rejoice before the LORD your God: you, your son, your daughter, your male servant, your female servant, the Levite who is within your gates, the foreigner, the fatherless, and the widow who are among you, in the place which the LORD your God shall choose to cause his name to dwell there.