There's a new book out,
Naming Infinity: A True Story of Religious Mysticism and Mathematical Creativity, that describes how a mystical Russian Orthodox sect, the "Name-Worshippers", help produce "one of the biggest mathematical breakthroughs of the twentieth century".
The "Name-Worshippers", the book claims, were deemed heretical by some Russian Orthodox leaders of the late Tsarist period. But, it appears, the Name-Worshippers were simply practicing the Jesus Prayer. So, why should the Jesus Prayer have been resisted by some Orthodox in the early 20th-century?