Leviticus 16:29-31

29And this shall be an everlasting statute unto you. In the seventh month, on the tenth of the month, ye shall afflict your souls, and do no work at all, the home-born, and the stranger that sojourneth among you;

30for on that day shall atonement be made for you, to cleanse you: from all your sins shall ye be clean before Jehovah.

31A sabbath of rest shall it be unto you, and ye shall afflict your souls: [it is] an everlasting statute.