Deuteronomy 16:8-10 New International Version - UK (NIVUK)
8 For six days eat unleavened bread and on the seventh day hold an assembly to the Lord your God and do no work.
The Festival of Weeks
9 Count seven weeks from the time you begin to put the sickle to the standing corn. 10 Then celebrate the Festival of Weeks to the Lord your God by giving a freewill offering in proportion to the blessings the Lord your God has given you.