Bede the Venerable

Mystically, by the first denial of Peter are denoted those who before our Lord’s Passion denied that He was God, by the second, those who did so after His resurrection. So by the first crowing of the cock His resurrection is signified; by the second, the general resurrection at the end of the world. By the first damsel, who obliged Peter to deny, is denoted lust, by the second, carnal delight: by one or more servants, the devils who persuade men to deny Christ.