In his book Jesus the King, Tim Keller describes the elaborate preparations the high priest had to make before he was able to go into the holy of holies to offer the required sacrifices on the mercy seat to atone for the sins of the people.
Only one priest was allowed to go into the holy of holies, and only on Yom Kippur, the Day of Atonement. A week before that day the high priest went into isolation to ensure he would not come into contact with anything or anyone that would render him unclean—and therefore unfit. “Clean” food was brought to him, and he would wash his body and prepare his heart during this week.
On the final night before the Day of Atonement, he did not sleep, but spent the night praying and reading Scripture to prepare and purify his soul. Finally, he would bathe from head to toe and dress in the pure, unstained white linen of his office. Only then would he be ready to enter the holy of holies and offer the sacrifice for his own sins.
Once he had done that, he would come out, bathe, put on fresh clean linen clothing, and reenter to offer sacrifice for the sins of the priests.
When that sacrifice was complete, he would come back out, bathe again, dress in fresh clean clothes, and reenter to offer sacrifices for the sins of the people.
Why all these preparations? Keller says, “Spiritually, morally, unless you’re clean, you can’t be in the presence of a perfect and holy God.” Habakkuk 1:13 explains that God is “pure and cannot stand the sight of evil.” Just read the book of Leviticus and you will understand just how far God will go to protect His own holiness, and the hoops that sinful men had to jump through to be allowed to approach Him.
That’s what makes Hebrews 4:16 so astonishing! How can we as sinful people “come boldly to the throne of our gracious God”? He is still the same holy God who still jealously protects His holiness. That hasn’t changed.
What has changed is that God “loved us and sent his Son as an atoning sacrifice for our sins” (1 John 4:10). “God made him who had no sin to be sin for us, so that in him we might become the righteousness of God” (2 Corinthians 5:21). God Himself became the sacrifice on our behalf. It is because of Him that the curtain guarding the holy of holies was torn (Matthew 27:51). It was because of Him that we can now come, unhindered, having been “washed,… sanctified,… justified in the name of the Lord Jesus Christ” (1 Corinthians 6:11). So we now come boldly before the throne of grace. But we should never forget that the reason we can do so is because Jesus died a horrible death in order to pay the penalty we so richly deserved. Come boldly, but never come presumptively. Come confidently, but come humbly. Come knowing that God says He will hear us when we pray (Psalm 55:17)