"May every bell toll, every adhan, every call to prayer blend into a single, soaring hymn," he said, using the Arabic term for the Muslim call to prayer.
Leo is near the end of his first overseas trip as Pope, a visit to Turkey and Lebanon, ancient biblical lands where he has championed the advancement of Christian and wider religious unity, and the cause of peace.
On Tuesday, in the final appearances of his trip, he will pray at the site of a deadly 2020 port blast that shredded swathes of Beirut, then lead a Mass on the city's historic waterfront with an expected 100,000 people.
Leo has described his trip to Lebanon, racked by years of conflict, political paralysis and economic misery, as a mission of peace, and in Turkey he warned that humanity's future was at risk due to the world's ongoing bloody conflicts.
The Pope met faith leaders on Monday in the central Martyrs' Square, situated on the "green line" that divided Muslim west and Christian east Beirut during the 1975-90 civil war, and urged them to be "builders of peace".
Lebanese representatives of the Alawite and Druze communities, which have suffered through bouts of sectarian violence in neighbouring Syria this year, spoke at the event.
In the crowd, Alawite Mohammed Saleh said his community needed peace, protection and dignity.
"We ask him humbly to remember in his prayer the Alawite community in the Middle East," Saleh said.
Later on Monday about 15,000 young people gathered for an event with the 70-year-old pontiff outside the Maronite Catholic headquarters.
"There is hope within you, a gift that we adults seem to have lost. ... You have more time to dream, to plan and to do good," he said.
Leo also visited the tomb of St Charbel, a Catholic saint revered across the region, before heading to Harissa, a Catholic shrine on a mountaintop overlooking the Mediterranean just north of Beirut.
People at the shrine, known for its towering statue of the Virgin Mary looking out towards Beirut, ululated as the pope arrived, pressing in to greet him with shouts of "Viva il Papa" (Long live the Pope).
"We have really been waiting for the Pope's visit because it is raising our hope now," said Revreend Toni Elias, a Maronite priest from Rmeich, a Christian town close to the Israeli border. The Maronites are an eastern-rite Catholic community and the largest Christian sect in Lebanon.
Before speaking at the shrine, Leo heard testimonies from people living in Lebanon. Loren Capobres, a Filipina migrant in the country for 17 years, told Leo about her experience living through war.
The Pope said stories like hers show the need to "take a stand to ensure that no one else will have to flee from his or her country due to senseless and cruel conflicts".
Lebanon, which has the largest share of Christians in the Middle East, has been rocked by the spillover of the Gaza conflict, as Israel and the Lebanese Shi'ite Muslim militant group Hezbollah went to war, culminating in a devastating Israeli offensive.
