Matthew 26:73 - Ellicott's Commentary On The Whole Bible

Thy speech bewrayeth thee. — The Galilean patois was probably stronger when he spoke under the influence of strong excitement. It was said to have, as its chief feature, a confused thick utterance of the guttural letters of the Hebrew alphabet, so that they could not be distinguished from each other, and the change of Sh into Th. The half-detection which the remark implied, perhaps, also, some sense of shame at the provincialism attracting notice, led to the more vehement denial that followed.