ISB ~ Matthew 26 v74

the cock crowed:Peter is unwilling to identify with Jesus and denies even knowing him. Hearing the cock, he recalls Jesus’ prophecy (26:34) and probably his foolish over-confidence (26:35). See note on Mt 26:34.

• Morally (St. Laurence Giustiniani, de Christi agone, chap. 9): Peter typifies man’s proneness to sin. The cock is the informed conscience that accuses us of sins, reminding us of God’s commandments and stirring the soul to contrition. As with Peter, the informed conscience directs sinners away from despair and toward genuine repentance.