When President Joe Biden meets with Pope Francis on Friday, he won’t kiss the ring.

Biden, who has met with Francis three times and with two previous popes, has said he eschews the traditional sign of respect because his mother told him not to — that no one is “better” than him. In their meeting, the two are expected to discuss issues like the COVID-19 pandemic and climate change as equals.

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Biden, only the second Catholic president in U.S. history, often speaks publicly about his faith and attends Mass every weekend.

As a second-term senator, Biden met with Pope John Paul II in 1980, when the two spent a reportedly chummy 45 minutes together. As vice president, he met with Pope Benedict XVI in 2011, when he famously told the pope to go easier on American nuns, who then were under fire by the church for activism on issues like poverty.

By all accounts, Biden has a positive relationship with the current pontiff, beginning when he attended Francis’ inauguration as pope in 2013. They also met during the pontiff’s 2015 visit, including a private meeting where Biden said the pope prayed for his family as they mourned the recent death of Biden’s son Beau. In 2016, they met again, when Biden spoke about cancer care at a conference on regenerative medicine at the Vatican.

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The president keeps a photo of one of his meetings with the pope behind his desk in the Oval Office. Their upcoming meeting continues a long tradition of president-and-pope encounters.

Some notable moments from meetings past:

—President John F. Kennedy’s 1963 meeting with Pope Paul VI at the Vatican was historic: The first Roman Catholic president of the United States was seeing the Roman Catholic pontiff only days after his coronation. Kennedy, who faced anti-Catholic bias during his presidential campaign, shook hands with the pope rather than kissing his ring, as is the usual practice for Catholics.

—Pope Paul VI’s trip to New York in October 1965 presented protocol problems. President Lyndon Johnson wanted to see him, but the pontiff was a chief of a state not officially recognized by the U.S. The solution: Johnson flew to New York for dinner at the apartment of his friend Arthur Goldberg, the U.S. ambassador to the United Nations, and the pontiff was welcomed to Johnson’s suite at the Waldorf-Astoria Hotel the next day.

—Johnson had a penchant for somewhat odd papal presents. At that 1965 meeting, his gifts to Paul included a silver-framed, autographed photograph of himself. Two years later, at their next meeting at the Vatican, Johnson presented the pontiff with a foot-high bust of himself.

—Jimmy Carter was the first president to play host to a pope at the White House. Pope John Paul II’s stay at the White House featured 10,000 guests — split between separate arrival and departure ceremonies on the North and South Lawns.

—President Ronald Reagan had trouble keeping his eyes open on his first visit to the Vatican in 1982. Reagan’s head bobbed and his eyes repeatedly closed for seconds at a time while John Paul talked solemnly of crises in the Falkland Islands and Lebanon. The incident came during a 10-day European trip with a packed schedule for Reagan. But it fed already rampant talk that the 71-year-old president wasn’t physically up to the job.

—Reagan sparked controversy over the separation of church and state in 1984 by establishing formal U.S. diplomatic relations with the Vatican, a long desire of the Holy See. Shortly afterward, Reagan and John Paul met during refueling stops at the airport in Fairbanks, Alaska (their paths were crossing as one finished and one began trips to Asia). The Alaska stop generated lots of excitement, but also scores of T-shirts reading “The Pope Meets the Dope.”

—For his last of four meetings with Pope John Paul, President Bill Clinton flew to St. Louis to greet the pontiff as he began a U.S. tour. Back in Washington, the Senate was in the throes of its impeachment trial against Clinton, and John Paul said “America faces a time of trial.” But it was generally assumed that the pontiff, who also challenged Americans to “a higher moral vision,” was speaking about his long-running and sharp dispute with Clinton over the president’s support for abortion rights.

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—At George W. Bush’s last meeting with John Paul, at the Vatican in June 2004, he presented the pope with the Medal of Freedom, the nation’s highest civilian honor. The pontiff responded by reading a statement about his “grave concern” over events in Iraq, where the U.S.-led war had been going on for just over a year.

—After John Paul died in 2005, Bush became the first sitting U.S. president to attend a papal funeral.

—At his first audience with John Paul’s successor, Pope Benedict XVI, Bush’s overly casual behavior was noted by many Italians and Vatican watchers. He addressed the pope as “sir,” rather than the customary “your holiness,” and leaned far back in his chair with one leg thrown informally over another, instead of the ramrod-straight physical posture more commonly seen in the pontiff’s presence. Rome’s ANSA agency flashed a “Gaffe Presidente” headline.

—For Benedict’s first U.S. tour as pope, there were several presidential firsts: Bush traveled to Andrews Air Force Base in Maryland to meet the pontiff’s plane, brought the largest crowd of his presidency to the South Lawn for Benedict’s arrival ceremony, and hosted a dinner in the pope’s honor that Benedict didn’t attend.

—Former President Barack Obama met with Pope Francis twice, once at the Vatican in 2014 and again during the pope’s 2015 visit to the U.S., where Obama met Francis on the tarmac at Andrews and played host in the Oval Office. Before 11,000 people on the South Lawn of the White House, Obama praised the pope as a “living example of Jesus’ teachings,” while Francis lauded Obama for his commitment to addressing climate change.

—Former President Donald Trump had a famously prickly relationship with Pope Francis. The two sparred during the 2016 campaign, with Francis taking a veiled swipe at Trump by declaring that people who think only of building barriers instead of bridges are “not Christian.” Trump, who campaigned on building a wall at the U.S.-Mexico border, called the comments “disgraceful” and suggested the Mexican government was using Francis as a pawn. When the two met at the Vatican in 2017, photos showed a stone-faced Francis standing next to a grinning Trump. The president later said their meeting had been “fantastic.”