At that moment the Lord turned and looked at Peter.
Up until that moment, Peter was riding high. He was tracking with his Lord. He was an undercover agent gathering critical intelligence about the events of his Master's arrest and torment. He was lying low and staying close.
He was a hero.
And then the rooster crowed and the bloodied Man Whom Peter loved turned and looked at him.
He'd denied being with the Lord to a servant girl, a servant of the high priest, and some bystanders. Nobodies. Peter didn't look the high priest in the eye and deny Jesus was the Christ. He cunningly kept his cover to servants and bystanders.
Jesus said we'd be judged by every little word said in passing, and here we see it. Jesus valued Peter's response to that servant girl. Denying Jesus to a servant girl was one with denying Him before Caesar. And He didn't brook spying as an excuse. Astounding.
Lord have mercy.