On the Day of Atonement, why did the high priest first take animal blood behind the veil?
On the Day of Atonement, the high priest first carried animal blood behind the veil into the Holy of Holies to sprinkle it on the mercy seat for his own sin. Only after that did he return with a second animal's blood to atone for the nation's sins.
Les explains that Hebrews chapter 9 rehearses the Day of Atonement. The high priest would enter the Holy of Holies behind the curtain first with the blood of an animal, sprinkling it on the mercy seat, or the Ark of the Covenant, for his own sin. He would then go back and take the blood of the second animal behind the veil, sprinkling it on the mercy seat to take care of the sins of the nation.