Leviticus 23:24, 39

Speak unto the children of Israel, saying, In the seventh month, on the first day of the month, shall be a solemn rest unto you, a memorial of blowing of trumpets, a holy convocation.

Howbeit on the fifteenth day of the seventh month, when ye have gathered in the fruits of the land, ye shall keep the feast of Jehovah seven days: on the first day shall be a solemn rest, and on the eighth day shall be a solemn rest.