The pope did not explain how the families had been chosen, but said: “They are guests of the Vatican.”  Francis also showed reporters two drawings given to him by children in the Moria camp. One showed children drowning in the sea. The other showed the sun crying.  “The children have these things in their minds, and it will take time before these memories go away,” the pope said. “If the sun is able to cry, so can we. A tear will do us good.”  While papal visits to refugee camps are not new, religious scholars said Francis’ rescue of the 12 Syrians sent an important signal that reflected his long history of affinity with the world’s most vulnerable, dating to his roots as a Jesuit priest in Argentina.  “Welcoming the stranger is the heart of the Christian message,” said Charles Camosy, a professor of Christian ethics at Fordham University in New York. While Francis is often seen as a progressive pope, Mr. Camosy said, he also is “pushing a more traditional understanding of what Christianity is all about.”  Francis’ first papal trip in 2013 was to the Italian island of Lampedusa, to call attention to the refugees who were arriving there from Libya — or drowning before they reached shore. During his February visit to Mexico, Francis prayed beneath a large cross erected in Ciudad Juárez, just footsteps from the border with the United States, and then celebrated Mass nearby, where he spoke about immigrants.  Upon landing in Lesbos on Saturday, Francis held a brief private meeting with Greece’s prime minister, Alexis Tsipras, before traveling across the island to the detention center in Moria, where people are held as they await rulings on their asylum applications — or as they wait to be deported under a recent agreement struck between the European Union and Turkey to curb migration.  Beginning last summer, hundreds of thousands of migrants, mostly from Syria, Iraq and Afghanistan, have poured into Lesbos after paying smugglers to make the short sea journey from Turkey. The procession through Greece and the Balkans toward Germany plunged the European Union into a political crisis and eventually led several countries to restrict or close their borders.  The deal with Turkey includes a provision under which migrants arriving in Greece can be swiftly deported back to Turkey. Since the deal took effect last month, the number of migrants arriving in Lesbos has dropped sharply (even as the numbers arriving in Italy are steadily rising). Critics say the agreement has trampled on the civil rights of refugees fleeing war and betrayed the ideals of the European Union.  At the migrants camp, Ecumenical Patriarch Bartholomew, the spiritual leader of the world’s Eastern Orthodox Christians, reminded Europeans and their leaders that Christians and others are judged on how they treat the powerless. “The world will be judged by the way it has treated you,” Bartholomew told the refugees. “And we will all be accountable for the way we respond to the crisis and conflict in the regions that you come from. The Mediterranean Sea should not be a tomb.”  Thousands of migrants have drowned in the Mediterranean, including a young child whose limp body washed ashore last year on the Turkish coast. A photograph of the child became a searing icon of the refugee crisis. “I hope that we never see children washing up on the shores of the Aegean Sea,” said Archbishop Ieronymos II, the leader of the Greek Orthodox Church, who called for a greater response by the United Nations. “I hope to soon see them there, untroubled, enjoying life.”  At the Moria center, Francis slowly walked down a line of migrants, many of them Muslims, greeting people as some waved handwritten signs with slogans like “Freedom of Movement.” Others propped their children above their shoulders or held out smartphones to photograph the pope.  Inside a large white tent, Francis greeted a woman in a head scarf as she cradled her baby, as well as other refugee families. A small boy stepped forward and handed him a picture drawn with crayons. An Iraqi mother asked Francis to help her find medical care for her child’s bone cancer. At one point, a man began wailing as Francis placed his hands on the man’s head. “Please, Father, bless me!” the man shouted. “Please, Father, bless me!”  Francis and the other religious leaders offered special praise on Saturday for ordinary Greeks who have welcomed refugees, taken some into their homes or provided food and clothing, even as they endure hardship amid the country’s long-running financial crisis. Mr. Tsipras and other Greek leaders have called on the European Union to provide more help to the country as it has borne the brunt of the migrant crisis.  Across Europe, the mood has soured in recent months, as many countries have closed or restricted their borders amid mounting public anxiety over the chaotic influx of more than a million refugees last year. The recent terrorist attacks in Paris and Brussels have also darkened public attitudes and stirred anti-migrant sentiment in some areas, even as many refugees say they are trying to escape extremist violence. Far-right, anti-immigrant parties have seized on the crisis to make gains, most recently in regional elections in Germany.  By appearing with the two Orthodox Christian leaders, Francis also took another small step in healing the breach between the Eastern and Western branches of Christianity. Francis has made ecumenical outreach a priority and in February became the first pope to meet with the patriarch of the Russian Orthodox Church.  Carlo Pioppi, a professor of church history at Santa Croce University in Rome, said the appearance by the three leaders showed they could put aside doctrinal and theological differences to highlight their shared concern about refugees. The three men described the refugee influx as one of Europe’s most serious crises since the end of World War II.  “Regular people will understand the sign these three religious leaders are sending,” Professor Pioppi said in an interview on Friday. “To see them have lunch with refugees, all together, is a strong message of humanity.”  The British charity Oxfam released a statement on Friday calling for a moratorium on deportations of refugees from Greece to Turkey until the authorities can guarantee that asylum processes are followed. The group also raised questions about new “fast track” processes to review asylum cases that the Greek Parliament recently approved under pressure from the European Union.  “Thousands are being held in squalid detention centers on the Greek Islands — this is the state of Europe in 2016,” Farah Karimi, the executive director of Oxfam Novib, the Dutch affiliate of Oxfam, said in the statement. “Shame on the E.U. for prioritizing detention and deportation over people’s rights to safety and dignity.”  Follow Jim Yardley on Twitter @JimBYardley.  Gaia Pianigiani contributed reporting from Rome, and Rick Gladstone from New York.  A version of this article appears in print on April 17, 2016, on page A1 of the New York edition with the headline: 12 Syrians Get Gift of Refuge From the Pope. Order Reprints| Today's Paper|Subscribe
The pontiff visited Lesbos, the heart of Europe’s migrant crisis, asking for deeper sympathy at a moment when attitudes are hardening.