todayinhistory:

October 31st 1517: Luther posts his 95 theses

On this day in 1517, the Augustinian monk Martin Luther posted
his 95 theses on the door of a Church in Wittenberg, Germany. This
event is generally considered the start of the Protestant Reformation.
The theses expressed Luther’s dissatisfaction with the corruption and
materialism of the Catholic Church, especially the sale of indulgences, which allowed prietss to essentially sell a ticket to heaven. Instead, Luther believed that
eternal salvation can only be guaranteed by God, and the modern church was too corrupt to provide true access to God. On the same day as
supposedly posting the 95 theses on the church door, Luther sent his
writings to several bishops. The writings were gradually translated and spread
throughout Europe, accelerated by the use of the printing press, and his
ideas transformed the religious landscape of Europe, leading to the Reformation and the establishment of
Protestantism.