Matthew 26:34

26:34 Jesus said to him, “I tell you the truth, ¹  on this night, before the rooster crows, you will deny me three times.”

Matthew 26:75

26:75 Then Peter remembered what Jesus had said: “Before the rooster crows, you will deny me three times.” And he went outside and wept bitterly. ² 

¹ tn Grk “Truly (ἀμήν, amhn), I say to you.”

² sn When Peter went out and wept bitterly it shows he really did not want to fail here and was deeply grieved that he had.