Charles Ellicott Commentary Mark 14:70

"But he again denied it. And after a little while again they that stood by said to Peter, of a truth thou art [one] of them; for thou art a Galilaean." — Mark 14:70 (ASV)

And thy speech agreeth thereto.—Strangely enough, the words, which seem so natural, are missing in many of the best manuscripts, and may, therefore, possibly have been an interpretative addition, possibly made by St. Mark himself, in what we may call a revised edition of his Gospel.