The famous line, "All is grace," is a quotation from Therese de Lisieux, a saint to whom novelist Georges Bernanos was deeply devoted.
According to the DVD's commentary, Claude Laydu felt repelled by Robert Bresson's directing methods. He claimed Bresson "would work on an actor, like a sculptor models his clay". The commentary says: "Bresson worked with Laydu every Sunday for a year, persuading him gradually into the role. He lived for many weeks with a group of young priests, absorbing their mannerisms and gestures, and during shooting he starved himself so as to acquire the authentic mask of undernourishment and illness."
The main character's bizarre, unhealthy eating habits, not to mention his obsessive isolation and loneliness, were reportedly an influence on the character of Travis Bickle in Taxi Driver: Motorista de Táxi (1976).