"You are going to get us killed with your archives," Michaeel's assistant Watheq Qassab grumbled as he struggled to carry six boxes of the documents dated between the 13th and 19th century across the border from Iraq into Kurdistan in August last year.
The Roman Catholic Dominican Order arrived in Iraq in the 13th century, and set up a permanent church in the second city of Mosul in 1750.
Michaeel first smuggled his precious library out of Mosul to Qaraqosh -- Iraq's largest Christian town -- during an Islamist insurgency in 2008 which saw thousands of Christians flee the city.
Last year, the friar again felt the tide turning as the Islamic State group seized town after town, destroying priceless artefacts and documents in museums and libraries in their rampage across Iraq and Syria.
As IS on Thursday seized the ancient city of Palmyra in Syria, raising fears of further destruction, Michaeel told AFP in Paris how he became obsessed with saving the remnants of Iraq's 2,000-year-old Christian heritage.
"It was imperative that these manuscripts, conserved in the Dominican library in Mosul and then in Qaraqosh, escape the systematic destruction of the non-Muslim cultural heritage," Michaeel told AFP.
-'I thought we were going to die'-
So, when IS seized Iraq's second city of Mosul in June, a short distance from Qaraqosh, Michaeel again took action.
"We loaded a large part of the manuscripts in a truck and drove them to Arbil, in Kurdistan, which is 70 kilometres (40 miles) away," he told AFP.
And when the jihadists descended on Qaraqosh on August 7, forcing the last Dominican friars to flee, he stashed the remaining manuscripts in boxes in his car.
"We were engulfed in the massive exodus of Christians and Yazidis who were fleeing to Arbil", the Kurdish capital, said Michaeel.
"We could see the black flag of Daesh (IS) from a distance. We were protected by armed peshmerga (Kurdish fighters) but they wouldn't let our car cross the border.
"So I started to take the boxes of manuscripts out of the car and hand them to passers by," he said.
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Watheq Qassab, an Iraqi working for the Dominican order, helped him.
"Bullets were whistling above our heads and I thought we were going to die," he told AFP.
"Children were crying, women too. I was carrying six boxes, it was heavy, I couldn't run."
Luckily, a car was waiting for them on the Kurdish side of the border, and all the boxes arrived safe and sound and are now hidden in Arbil.
Michaeel's collection includes historical and philosophical texts, documents on both Christian and Muslim spirituality, music and literature written in Aramaic, Syriac, Arabic and Armenian.
They bear testament to the long Christian tradition in former Mesopotamia -- seen as the cradle of Western civilisation -- which survived even as most of the region between the Tigris and Euphrates rivers converted to Islam in the 7th century.
Tens of thousands of Christians have been forced to flee what Pope Francis called the "intolerable brutality" being inflicted on them and other minorities in Iraq and Syria by IS group militants.
- 'Bridge between civilisations' -
Historian Francoise Briquel-Chatonnet, a researcher at the French National Centre for Scientific Research, said there were about 50 manuscripts written in the ancient Christian language of Syriac, dated "before the arrival of Islam in the same region."
"Most are conserved in the British Library in London. The oldest dates back to 411."
Michaeel's collection is not that old, but "they are a sort of bridge between civilisations, they bear witness to the past and say a lot about the present," said the friar, adding he sees them as his "children."
In Qaraqosh, Michaeel and his staff have been working for years to collect and digitise the ancient manuscripts, photographing them and storing them on a hard drive.
"Since 1990 we have digitised 8,000 manuscripts from the region. Half of the originals no longer exist as they have been destroyed by the Islamic State," he said.
Copies of seven of these documents are currently being displayed at the National Archives in Paris at an exhibition entitled: "Mesopotamia, a crossroads of cultures."