Leviticus can also be called “The Book of the Law of the Priests” as it contains very little historical matter, concerning itself with priestly legislation and the practice of the Law among the people. Much importance is placed upon Israel’s separation from all heathen influences so that the nation may retain its religious purity.

Leviticus 23

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.