Speaking at the Church of the Immaculate Conception in the town of Qaraqosh, Francis stressed that "forgiveness" is an important principle for Christians even in the face of destruction at the hands of the terrorist group.
"The road to full recovery may still be long, but I ask you, please do not grow discouraged," he said." What is needed is the ability to forgive but also the courage not to give up."
Earlier in the day, the pope lamented "the blood spilled by those who pervert the name of God to pursue paths of destruction" as he spoke amidst the ruins of four churches in Mosul
"Here in Mosul, the tragic consequences of war and hostility are all too evident," he said. "How cruel is it that this country, the cradle of civilization, should have been afflicted by so barbarous a blow, with ancient places of worship destroyed and many thousands of people -- Muslims, Christians, Yazidis, who were cruelly eliminated by terrorism, and others -- forcibly displaced or killed."
IS seized Mosul in 2014, including many Christian towns in the region, and killed thousands of people and destroying many historical sites, forcing survivors to flee.
The square where he spoke Sunday previously housed the Syriac Catholic, Armenian-Orthodox, Syriac Orthodox and Chaldean churches but now holds just their hollowed remains.
On Sunday, however, Francis declared that the forces that bring people together are stronger than those that tear them apart.
"We reaffirm our conviction that fraternity is more durable than fratricide, that hope is more powerful than hatred, that peace is more powerful than war," he said.