Mark 14:71

71 He began to call down curses, and he swore to them, “I don’t know this man you’re talking about.”

Read Mark 14:71 Using Other Translations

But he began to curse and to swear, saying, I know not this man of whom ye speak.
But he began to invoke a curse on himself and to swear, "I do not know this man of whom you speak."
Peter swore, “A curse on me if I’m lying—I don’t know this man you’re talking about!”