The Vow(1973)

Original title: A Promessa

José and Maria, a young, devout couple in a remote Portuguese fishing village, take a vow of chastity on their wedding night to honor a religious pact. Their commitment is pushed to the breaking point when they rescue a mysterious, wounded stranger and bring him into their home. As the outsider’s presence ignites repressed desires and jealousy, the couple's sacred promise leads to a violent confrontation with the local community's superstitions.