Look in a Russian Orthodox (or Greek Orthodox) Church calendar, which gives the saints commemorated on each day of the year, and you will find this entry:
Dec 02 / Nov 19: Venerables Barlaam and loasaph, Prince of India, and Saint Abenner the King, father of St. loasaph (4th c.).
The interesting thing about that entry is that Ioasaph/Ioasaf, Prince of India, is actually the Buddha. Yes, you read correctly: the Buddha. The Eastern Orthodox Church annually commemorates the Buddha in their calendar of saints.
Of course the reason for this is that until relatively recently, no one in Eastern Orthodoxy knew that Ioasaph was the Buddha. But that is the inescapable conclusion of scholars who have studied the matter, and the reason for it turns out to have been rather simple.
In early times, Buddhist missionaries were found on parts of the trade route extending from the West all the way to India. And so stories of the life of the Buddha became spread here and there, and one of those stories — the story of the Buddha’s early life — came West. It is the tale of a young Prince of India who decides to renounce his wealth and power for the spiritual life.
When Christians encountered this tale, it became distorted into the story of a Prince of India who renounced his wealth and power for Christianity, and that, in brief, is how the Buddha came to be a Christian saint commemorated in the Eastern Orthodox calendar.
The name “Ioasaph” — also found as Ioasaf, Joasaph and Josaphat — is simply a garbled version of the word “Bodhisattva” — the title applied to the Buddha before his enlightenment. The identity becomes more clear if one sees the Arabic intermediate forms Budasaf and Iudasaf. Barlaam — written as “Varlaam” on Russian icons — was a pious hermit who counseled Ioasaph.
The story of Barlaam and Ioasaph in Greek was once attributed to the 7th century John of Damascus (the big supporter of icon veneration), but apparently the core was actually transmitted earlier through Manichaean writings on the trade route. A christianized version comes from the Balavariani, a 10th century Georgian epic; Euthymios of Athos, a Georgian monk, translated the story into Greek in the early 11th century. It can be traced back through an Arabic version to early Sanskrit Mahayana texts recounting the life of the Buddha. In its Greek version — the one still considered “history” by countless Orthodox believers — it is called The Precious Pearl.
Sunday, December 2:
27TH SUNDAY AFTER PENTECOST—PROPHET OBADIAH OF THE 12, MARTYR BARLAAM OF CAESAREA IN CAPPADOCIA, MARTYR HELIODORUS IN PAMPHYLIA, MARTYR AZES IN ISAURIA & 150 SOLDIERS WITH HIM, VENERABLE BARLAAM & IOSAPH PRINCE OF INDIA & HIS FATHER SAINT ABENER THE KING, VENERABLE HILARION-MONK & WONDERWORKER OF GEORGIA, VENERABLE BARLAAM-ABBOT OF PECHERSKY LAVRA, SAINT PATROCLUS OF BOURGES IN GAUL
Eastern Orthodoxy has a very strong attachment to tradition (one of the chief sources, in fact, of its doctrines and lore of saints and icons), but it has never had a clear boundary between higher and lower traditions, nor has it ever been particularly careful or scrupulous about actually checking the veracity of those traditions, as this one out of many examples illustrates. As one person on the Internet remarked concerning this mistaking of the Buddha for a Christian saint, “Saint….OOPS!” Eastern Orthodox bookstores still sell the life of Sts. Varlaam and Ioasaph.
Those who want a more detailed account of the transmission and transformation of the story of the Buddha into that of a Christian saint will want to read the book In Search of the Christian Buddha: How an Asian Sage Became a Medieval Saint, by Donald S. Lopez Jr. and Peggy McCracken, W.W. Norton & Co, 2014.