Mass of the Rooster is the name given by Catholics to Mass celebrated on Christmas Eve that begins at midnight from December 24 to 25. The phrase “Mass of the Rooster” is specific to Latin countries and derives from the ancestral tale that at midnight on December 24, a rooster would have sung strongly, as never heard before from another similar animal, announcing the coming of the Messiah, son of God, Jesus Christ.
Another tale, of Spanish origin, says that before hitting the 12 rings of the bell at midnight on December 24, each farmer of the province of Toledo in Spain killed a rooster in memory of the one who sang when St. Peter denied Jesus three times, at the time of his death. The bird was then taken to the Church to be offered to the poor who thus saw their Christmas improve. It was customary, in some Spanish villages, to take the rooster to the church to sing during the Mass, signifying a harbinger of good harvests. But that was formerly because now this is forbidden.
The mass of the rooster is usually celebrated with great joy, as it is told in the text about the tradition of the Mass of the Igreja da Lapa.