This image of Aleksei A. Navalny’s body in a coffin, at a church in southern Moscow, conveys many of the traditions of the Russian Orthodox Church, an institution that has bound itself closely to the Kremlin but that also counted opposition figures, including Mr. Navalny, among its faithful.

“I, to my shame, am a typical post-Soviet believer,” Mr. Navalny said in an interview in 2012. “I keep fasts, I got baptized at church, but I go to church quite rarely.”

Being an Orthodox Christian, he said, made him feel “like I am part of something big and shared.”

He added: “I like that there are special ethics and self-restraints. At the same time, it doesn’t bother me at all that I exist in a predominantly atheistic environment. Until I was 25 years old, before the birth of my first child, I myself was such an ardent atheist that I was ready to grab the beard of any priest.”

Those remarks reflected the circumstances of many Russians who came of age as the Soviet Union broke apart and as the Russian Orthodox Church again rose to prominence in public life.

Over the last two decades, the church has tied itself closely to the increasingly conservative and nationalist views espoused by President Vladimir V. Putin. That has forced critics like Mr. Navalny, and pockets of progressive believers, to try to reconcile their political dissent and their faith.

The church in southern Moscow where the Mass was held — the Church of the Icon of the Mother of God Soothe My Sorrows — is not far from where Mr. Navalny lived until 2017 and where his family had an apartment.