Hebrews 10:22:

Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water.

See also:

Who You Are and What You Have
If You Blow It
Doesn’t 1 John 3:22 Prove That Our Ability to Receive Depends On How Well We Keep God’s Commandments?
Does Sin in My Life Stop Me from Getting Healed?
Is It Possible for a New Testament Believer’s Prayer to Receive Healing to be Hindered?
Objection: Old Testament Sacrifices Were Not Made Sick Before They Died, but They Still Covered Sins