God has revealed Himself through three books: nature, the sanctuary service, and the Bible. The sanctuary service, found in the Old Testament, prefigured Jesus' ministry in the heavenly sanctuary and provided a way for people to understand prophecy and the plan of salvation. On the Day of Atonement in 1844, Jesus entered the Most Holy Place of the heavenly sanctuary to begin the final cleansing of sins, as foretold in Daniel 8:14.