Charles Spurgeon Commentary Luke 22:58-60

"And after a little while another saw him, and said, Thou also art [one] of them. But Peter said, Man, I am not. And after the space of about one hour another confidently affirmed, saying, Of a truth this man also was with him; for he is a Galilaean. But Peter said, Man, I know not what thou sayest. And immediately, while he yet spake, the cock crew." — Luke 22:58-60 (ASV)

And after a little while another saw him, and said, Thou art also of them. And Peter said, Man, I am not. And about the space of one hour after another confidently affirmed, saying, Of a truth this fellow also was with him: for he is a Galilaean. And Peter said, Man, I know not what thou sayest.

Matthew and Mark tell us that, to prove this statement, and to make it quite clear that he was not a follower of Christ, he began to curse and to swear, as if the best evidence that he was not a Christian would be afforded by his cursing and swearing.