A cleansed conscience produces assurance, the fullest and unwavering confidence, to approach God. The OT cleansing or sprinkling with blood related only to that which was external, and could not make the conscience perfect.
Let us draw near to God with a sincere heart in full assurance of faith, having our hearts sprinkled to cleanse us from a guilty conscience and having our bodies washed with pure water (Hebrews 10:22 NIV).
The body, once polluted with sin, is washed with “pure water,” a symbol for the Holy Spirit. The OT counterpart was the Israelites outward consecration through the washing of their clothing prior to entering into the presence of God, becoming a nation, and receiving the Ten Commandments.
And the LORD told Moses, “Go to the people and purify them today and tomorrow. They must wash their clothes and be prepared by the third day, for on the third day the LORD will come down on Mount Sinai in the sight of all the people (Exodus 19:11).
Moses took the blood, sprinkled it on the people, and said, “This is the blood of the covenant that the LORD has made with you concerning all these words” (Exodus 24:8).
The Old Covenant was confirmed by the outward sprinkling of animal blood by Moses; the New Covenant by the inward sprinkling of Christ’s blood by the Holy Spirit.