My Night at Maud's(1969)

Original title: Ma nuit chez Maud

Devout Roman Catholic Jean-Louis subscribes to an austere moral code influenced by the philosophy of 17th-century physicist Blaise Pascal. When he spots a pretty girl at church, he promises to one day marry her. But then an old friend introduces him to alluring divorcee Maud. After a conversation about love and credo, the chaste Jean-Louis spends the night at Maud's, conflicted about his desires.