Bible Verses About The Sacred Vail: Allowed to enter but once a year

yea, Jehovah saith unto Moses, `Speak unto Aaron thy brother, and he cometh not in at all times unto the sanctuary within the vail, unto the front of the mercy-seat, which is upon the ark, and he dieth not, for in a cloud I am seen upon the mercy-seat.

and into the second, once in the year, only the chief priest, not apart from blood, which he doth offer for himself and the errors of the people,