Hebrews 10:19 (CSB) Therefore, brothers and sisters, since we have boldness to enter the sanctuary through the blood of Jesus --

Why does the blood of Jesus give us access to sanctuary? It is His blood that is sprinkled onto the mercy seat of God's covenant that gives us access to God's fellowship (Leviticus 16:11-14). It is because Jesus died on the cross that the curtain to the most holy place of God's fellowship was split from the top down (Matthew 27:51).  His blood continues to be the only blood that can give us access to God. The blood of bulls, goats, and sheep could only cover accidental sin for a year and had to be reapplied if one person sinned on purpose. But now Jesus' blood cleanses all sin for all time for all those who would accept it. (Leviticus 4:3,13-14, 22-23,27-28, Exodus 30:10, Hebrews 9:7,12, John 3:16, John 14:6)