When Luther appeared at the Diet of Worms on April 15–18, the assembly had already been meeting for nearly three months. At first, Luther was not scheduled to appear. He was summoned after he publicly burned the papal bull Exsurge Domine on December 10, 1520. The bull, drafted largely by Eck and issued by Pope Leo X in June, listed forty-one charges against Luther and threatened his excommunication if he did not recant his teachings against some of the actions and teachings of the church, particularly as they pertained to the sale of indulgences to fund the construction of St. Peter’s Basilica in Rome. Luther burned the papal bull in response to Eck’s burning of Luther’s books throughout Germany. Luther’s refusal to repent prompted Leo to excommunicate Luther in another papal bull titled Decet Romanum Pontificem on January 3, 1521. However, Luther remained under the protection of the elector of Saxony, Frederick III, which gave him freedom to preach and teach throughout the Saxon region. Luther’s audacious actions fueled the growth of his teachings’ popularity, leading many churches throughout the region to support and follow him.