Leviticus 16
16 Ref And let him make the holy place free from whatever is unclean among the children of Israel and from their wrongdoing in all their sins; and let him do the same for the Tent of meeting, which has its place among an unclean people.
17 Ref And no man may be in the Tent of meeting from the time when Aaron goes in to take away sin in the holy place till he comes out, having made himself and his house and all the people of Israel free from sin.
18 Ref And he is to go out to the altar which is before the Lord and make it free from sin; and he is to take some of the blood of the ox and the blood of the goat and put it on the horns of the altar and round it;
19 Ref Shaking drops of the blood from his finger on it seven times to make it holy and clean from whatever is unclean among the children of Israel.