“But Peter began
He swore an oath.
‘I do not know
You are talking about.’”
ὁ δὲ ἤρξατο ἀναθεματίζειν καὶ ὀμνύναι ὅτι Οὐκ οἶδα τὸν ἄνθρωπον τοῦτον ὃν λέγετε
This is almost word for word in Matthew, chapter 26:74. There is something similar in Luke, chapter 22: 60, and John, chapter 18:27. However, Luke did not have the curse or the oath, while John said that Peter simply denied Jesus. Mark said that Peter began to curse (ὁ δὲ ἤρξατο ἀναθεματίζειν). He swore an oath that he did not know this man (καὶ ὀμνύειν ὅτι Οὐκ οἶδα τὸν ἄνθρωπον) that they were talking about (τοῦτον ὃν λέγετε). Thus, we have the 3rd public denial of Jesus by Peter that can be found in all 4 gospels. This great apostolic leader had failed his first major test just as Jesus had predicted, despite his bombastic earlier outbursts that it would never happen. Are you sometimes too bombastic?