The London from which Handel created most of his wondrous art was the most religiously tolerant city in the world at that time.
17th Century England had seen the great Civil War, the Cromwellian Commonwealth and scores of thousands of deaths in religious wars and disputes.
The 18th, the century in which Handel composed music in England from 1710 to 1752, still struggled over religious rights of those not adhering to The Church of England. But Handel's London sheltered Christian religious dissenters from Europe (many on their way to the American colonies), Catholics and Jews.
From day to day, Handel wasn't a notably religious person. None of his Italian language operas - unlike Verdi's, for instance - touch upon biblical subjects. But his great late creations, the mature English language oratorios are on biblical subjects, most taken from the Old Testament.
Many think that The Messiah was Handel's first oratorio. It wasn't. It was his first huge blockbuster oratorio. Its success, coupled with Handel's frustrations over the costs of mounting staged operas (oratorios have no costumes, sets, expensive special effects and even more expensive Divas) led him to devote most of the energy of the last 15 years of his creative life to the composition and production of oratorios.
Up until Handel's oratorios, no composer had created masterpieces that might inspire Catholics, Protestents and Jews alike. But Handel's Old Testament oratorios did just that. He even went further in the oratorio, Judas Maccabeus, which recounts the events that led to the contemporary celebration of Hannukah.
Here's the duet and Chorus, Hail, Hail Judea, Happy Land:
Handel's most successful ecumenical oratorio was Israel in Egypt. Here is the chorus, Sing Ye to the Lord:
One might say that the ecumenism of Handel transcended his life in ways he couldn't have known. My favorite over-the-top version of his most famous oratorio movement, the Hallelujah Chorus from The Messiah, is this rendition by The Mormon Tabernacle Choir, representing a religion that didn't yet exist when Handel penned the masterpiece: