Patriarch Louis Raphaël Sako, the head of Iraq's Chaldean Catholic Church, is leading his country's Christians in a three-day fast for peace in Iraq, the Holy Land, and the wider world.

The fast, held every year in the run-up to Lent, is known by Syriac Christians--ancient communities concentrated in the Middle East--as the Baotha d'Ninwaye or "Petition of the Ninevites."

Related: Jonah, the Whale, the Assyrians, Christianity and Islam

This year, most Syriac Christians are observing the fast on 22-24 January.

Patriarch Sako, whose Chaldean Church is one of the larger Syriac Churches, is calling on the faithful to offer the fast up to God "for peace and stability in Iraq, the Holy Land, Ukraine, and the world."

The Patriarch -- whom Pope Francis created cardinal in 2018 -- called on believers to "fervently pray to God Almighty to inspire world leaders to seek peace and not war... and to achieve fruitful progress towards reconciliation, fraternal relations, love, and tolerance for the good of humanity."

The "Petition of the Ninevites"

The Nineveh Fast is held every year to mark the three days that the prophet Jonah spent in the belly of a whale. It's also a commemoration of the fasting in the city of Nineveh after its inhabitants accepted Jonah's call to repentance.

Many Syriac Christians abstain from all food and drink from midnight to noon on each of the three days. Others avoid meat or animal products for the entirety of the period, or do not eat at all.

Syriac Christian communities, which draw from theological and liturgical traditions in the Syriac language rather than in Latin or Greek, date back to the earliest days of Christianity.

Devastated by war and instability, they maintain a tenuous foothold in the Middle East. There are also large communities in south-western India and in the diaspora.

Syriac is a dialect of Aramaic, the language of Jesus, which was once spoken across the region.