Well, Chopin beliefs were quite of a mystery, but it is known that if he was a religious person, he almost never showed it in public, though Liszt once said that Chopin has a strong connection to religion, only privately. This piece is supposedly a reference about a song, (maybe in two parts) that Chopin wrote in 1846, based on the Veni Creator, and kept it private and only performed it in a wedding of his best friends. This is supposedly a copy by a person that was in that wedding and he inscribed the song that Chopin played there, But we need more evidence to know for sure.