Answer: Nicaea
Explanation: Before Milan Edict 313 AD, when Christianity became an equal religion of the Roman Empire with other religions, it was the so-called period of early Christianity. In early Christianity, there were no classified gospel books that made up the so-called official Bible. There were many different gospels, including the Gnostic ones, that is, early Christianity involved many different variants, teachings and interpretations. When Christianity became permitted in 313 AD, open discussions began, since Christians were no longer persecuted, which gospels were authentic, which were not, which should be read in the church, which were heretical, which were not, etc.
To end these discussions, the First Ecumenical Council was held in Nicaea 325 AD, where it was decided that the four Gospels should be included in the official Bible, as well as the Acts of the Apostles, Epistles, and Revelation. Thus, the discussions, at least those open and public, ceased. All other books and Gospels from early Christianity, except those I mentioned, were banned and even declared heresy. Thus the so-called official version of Christianity, recognized by Council emerged, and early Christianity ceased to exist. In this way, the strife and waste of energy on various conflicts over the truth and authenticity of the Gospels ceased, and official Christianity began to strengthen, relying on the official decision of the Nicaea Council.
