Matthew 18:16

18:16 But if he does not listen, take one or two others with you, so that at the testimony of two or three witnesses every matter may be established. ¹ 

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 

[18:16]  ¹ sn A quotation from Deut 19:15.

[26:75]  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.