Leviticus 23:41
And ye shall keep it a feast unto the Lord seven days in the year. It shall be a statute for ever in your generations: ye shall celebrate it in the seventh month.
Cross-reference
Numbers 29:12
Parallel
Numbers 29:12 provides details for the same seven-day feast of the seventh month, directly parallel to this command.
Nehemiah 8:18
Historical context
Nehemiah 8:18 describes the observance of the seven-day feast and solemn assembly, exactly as commanded here.