They will give thanks to the Almighty for the restoration of a sacred building whose resurrection has come to be seen as the triumph of Russia and its Orthodox Church over decades of Communist atheism.
But they will owe a debt to some rather more secular bodies. If they are to be fair, the devout should spare a prayer for the makers of such icons of Western consumerism as Coke and the Big Mac. The really zealous veruyushi (believers) might also consider firing off a praise-be or two for the sale of Russian weaponry.
Stalin, an enthusiastic destroyer of churches, flattened the cathedral in 1931, intending to build a huge Palace of Soviets, but he was interrupted by the Second World War. Khrushchev turned the place into a swimming pool.
Now, 20 months after its cornerstone was laid anew, the cathedral's golden domes are shining over the city again. With the structure virtually complete, Moscow officials face two pressing challenges: decorating its massive exterior, hopefully before the city's 850th anniversary next year, and finding people to pay the estimated pounds 200m final bill.
Despite widespread scepticism, the city authorities insist all of the money is coming from charitable donations, rather than from Russian federal or municipal budgets. Those who have chipped in, like latter-day Medicis, include several of the West's mightiest corporations, which have their sights fixed on further investment in Russia.
Among the several hundred statues that will eventually adorn the cathedral's exterior will be eight figures, including images of Christ, the Virgin Mary and St Thomas the Apostle, who owe their presence to a $100,000 (pounds 70,000) gift from Coca-Cola.
"We see it as an act of good citizenship," said a spokesman for Coke, which has a dozen plants in Russia. (No, she made clear, there will be no sign of advertisements about the world living in perfect harmony.)
When night falls, the building will be flooded in light, courtesy of a system provided free by Philips Electronics. The lavatories have been kitted out by a Belgian company; McDonald's, which has a chain of outlets in Moscow, has chipped in about $100,000. Russia's state arms exporter, Rosvoruzhenie, gave around pounds 100,000.Reuse content