Bede the Venerable — as excerpted in the Catena Aurea on Mark 14:66-72

“(ubi sup.) How hurtful is it1 to speak with the wicked. He denies before infidels that he knows the man, whom amongst the disciples, he had confessed to be God. But the Scripture is wont to point out a Sacrament2 of the causes of things, by the state of the time; thus Peter, who denied at midnight, repented at cock crow; wherefore it is added: And the second time the cock crew. And Peter called to mind the word which Jesus said unto him, Before the cock crow twice, thou shalt deny me thrice. And he began to weep.”