09. The First Council of the Lateran, 1123 A.D.
The First Council of the Lateran was the 9th ecumenical council recognised by the Catholic Church. It was convoked by Pope Callixtus II in December 1122, immediately after the Concordat of Worms. The council sought to bring an end to the practice of the conferring of ecclesiastical benefices by people who were laymen, free the election of bishops and abbots from secular influence, clarify the separation of spiritual and temporal affairs, re-establish the principle that spiritual authority resides solely in the Church and abolish the claim of the Holy Roman Emperor to influence papal elections.
The council was significant in size: 300 bishops and more than 600 abbots assembled at Rome in March 1123, and Callixtus II presided in person. During the council, the decisions of the Concordat of Worms were read and ratified. Various other decisions were promulgated.
Source: Wikipedia, Creative Commons Attribution-ShareAlike License 4.0