Albert Barnes Commentary Matthew 26:73

"And after a little while they that stood by came and said to Peter, Of a truth thou also art [one] of them; for thy speech maketh thee known." — Matthew 26:73 (ASV)

And after a while. That is, about an hour later (according to Luke). Peter, by this time, had returned to the palace or hall and stood warming himself by the fire (John 18:25).

Thy speech betrayeth thee. Your language makes it manifest that you are one of his companions. That is, as Mark adds, he was a Galilean; and in this way his speech betrayed him. It is probable that the Galileans were distinguished by some peculiarity of pronunciation, perhaps a certain rustic quality or coarseness in their manner of speaking, that set them apart from the refined speech of the capital, Jerusalem. This charge, as John relates (John 18:26), was supported by the express affirmation of a kinsman of Malchus, the high priest's servant, that he had seen him in the garden.