Overview of the Spring Festivals - Passover and Days of Unleavened Bread. The sermon begins with the convoluted history of Lent, a season that does not find its origin in the Bible, but in church tradition. The Spring Festivals have their origin in the Bible beginning with Passover - the most solemn occasion of the Christian year, the anniversary of the death of our Lord and Savior Jesus Christ to atone for our sins.