Fragments of the forgotten heretical document have been discovered at the University of Oxford library by Biblical scholars from the University of Texas at Austin.
The fragments come from 13 leather-bound vellum codices which had been buried in Egypt and found in 1945.
The documents detail the ‘First Apocalypse of James’ in which Jesus passes on knowledge of Heaven and future events to his brother, or possible step-brother, James, including the death of the younger sibling.
However, the documents were “forbidden” by early Christians as they would have had to have been added to the New Testament which was not permitted 1,600 years ago when the text was originally written.
Athanasius, Bishop of Alexandria, in his “Easter letter of 367” that defined the 27-book New Testament: “No one may add to them, and nothing may be taken away from them.”
The manuscript is from an early Christian form known as Gnosticism which still remains a mystery to researchers.
Study co-author Dr Geoffrey Smith, a scholar of Biblical Greek and Christian origins, said: “To say that we were excited once we realised what we had found is an understatement.
“We never suspected that Greek fragments of the First Apocalypse of James survived from antiquity. But there they were, right in front of us.
“The text supplements the biblical account of Jesus’s life and ministry by allowing us access to conversations that purportedly took place between Jesus and James — secret teachings that allowed James to be a good teacher after Jesus’s death.”
Brent Landau, a lecturer in the UT Austin Department of Religious Studies, added: “The scribe has divided most of the text into syllables by using mid-dots. Such divisions are very uncommon in ancient manuscripts, but they do show up frequently in manuscripts that were used in educational contexts.”