An ancient piece of papyrus that contains a mention of Jesus' wife is not a forgery, according to a scientific analysis of the controversial text, US researchers said.
The fragment, known as the "Gospel of Jesus' Wife", is believed to have come from Egypt and contains writing in the Coptic language that says: "Jesus said to them, 'My wife...'"
Another part reads: "She will be able to be my disciple."
Its discovery in 2012 caused a stir. Christian tradition has long held that Jesus was not married and the fragment renewed debates over celibacy and the role of women in the church.
The Vatican's newspaper declared it a fake, along with other scholars who doubted its authenticity based on its poor grammar, blurred text and uncertain origin.
Never before has a gospel referred to Jesus being married, or having women as disciples.
But analysis of the papyrus and the ink - as well as the handwriting and grammar - show the document is ancient, although the origin, context and exact meaning of the text is not known.
"No evidence of modern fabrication ('forgery') was found," the Harvard Divinity School said in a statement on Thursday.
The palm-sized fragment probably dates to between the sixth and ninth centuries, and could have been written as early as the second century, said the study results published in the Harvard Theological Review.
Radiocarbon dating of the papyrus and a study of the ink was carried out by experts at Columbia University, Harvard University and the Massachusetts Institute of Technology.
"The team concluded the papyrus' chemical composition and patterns of oxidation are consistent with old papyrus by comparing the GJW (Gospel of Jesus' Wife) fragment with a fragment of the Gospel of John," said the study.
"Current testing thus supports the conclusion that the papyrus and ink of GJW are ancient."
The origin of the papyrus is unknown. But Karen King, a historian at Harvard Divinity School, who received the fragment from an anonymous collector in 2012, stressed the science showing the papyrus is ancient does not prove that Jesus was married.
"The main topic of the fragment is to affirm that women who are mothers and wives can be disciples of Jesus - a topic that was hotly debated in early Christianity as celibate virginity increasingly became highly valued," King said in a statement.
The fragment measures 4cm by 8cm. Its crude appearance and grammatical errors suggest the writer had no more than an elementary education, King said.
Leo Depuydt, a professor of Egyptology at Brown University, wrote an article, also published in the Harvard Theological Review, explaining why he still thinks the document is a fake.
"The papyrus fragment seems ripe for a Monty Python sketch," he wrote.
He noted the grammatical errors and that the words "my wife" appear to be emphasised in bold letters, which do not feature in other ancient Coptic texts.
He wrote: "As a student of Coptic convinced that the fragment is a modern creation, I am unable to escape the impression that there is something almost hilarious about the use of bold letters."
King published a rebuttal to Depuydt's criticisms, saying in part that blotted ink was common and that the letters below "my wife" are even darker.