'Day of Atonement' in the Bible

"Also the tenth day of the self seventh month, is a day of atonement, and shall be a holy feast unto you, and ye shall humble your souls and offer sacrifice unto the LORD.

Moreover ye shall do no work the same day, for it is a day of atonement to make an atonement for you before the LORD your God.

And then thou shalt make a horn blow: even in the tenth day of the seventh month, which is the day of atonement. And then shall ye make the horn blow, even throughout all your land.