Lev 16:16 refers to the need to cleanse all the sins in the sanctuary by making an atonement on the day of atonement. Are these the sins that were transferred daily through the lamb sacrifices? How did these sins get into the sanctuary or did OT sanctuary service operate according to a substitute model where sins were transferred to the lamb, and from it to the sanctuary?
According to the last sentence of Leviticus 16:16 the tabernacle became defiled with sin simply by being in the midst of the unclean nation. The High Priest had to make atonement for both the Holy of Holies and the Tabernacle as a whole to cleanse them each year on the Day of Atonement (Yom Kippur).