Would the cock crow once or twice before Peter denied Jesus three times?

Mark gives the fuller detail; the other Gospels give the essential point. Jesus warned Peter that before the night’s cock-crowing was over he would have denied him three times. Mark, whose Gospel early tradition links with Peter’s own preaching, records the precise form, “before the cock crow twice” (Mark 14:30), and notes both crowings (14:68, 72). Matthew, Luke and John give the warning in its shorter form and mention only the crowing that mattered: the one that came as Peter finished his third denial and brought Jesus’ words back to him (Matthew 26:74–75; Luke 22:60–61).

The shorter form is not wrong, because ‘cock-crow’ was a recognised time of night: Mark names it as one of the night’s four watches, “at the cockcrowing” (Mark 13:35; Greek alektorophōnia), between midnight and about three in the morning. A cock may crow once and then crow in earnest later, and Gill notes that the second crowing was ‘properly the cock crowing’. To say ‘before the cock crows you will deny me three times’ is true if the third denial comes before that main crowing, as it did. Mark’s ‘twice’ adds precision rather than a different prediction, and no Gospel says that the cock crowed only once.

Two warnings

Luke and John place Jesus’ warning in the upper room (Luke 22:34; John 13:38), while Matthew and Mark place it on the way to the Mount of Olives (Matthew 26:30–34; Mark 14:26–30). Some harmonists think Jesus warned Peter more than once that night, in slightly different words. The answer above does not depend on this.