What does Matthew 26:72 mean?

Peter has been accused, for the second time, of being associated with the now-condemned Jesus (Matthew 26:69–71). Since Peter is in the courtyard of the high priest's house, he recognizes that he is in real danger (Matthew 26:64–66).

For the second time, Peter denies any association with Jesus. He swears by an oath not merely that he is not a follower, but that He does not even know Jesus, at all. The use of an oath means Peter swears by something sacred that he is telling the truth. Peter likely remembered well that Jesus had condemned exactly this kind of oath-swearing, saying instead, "Let what you say be simply 'Yes' or 'No'; anything more than this comes from evil" (Matthew 5:37).

Peter's oath and denial shows how desperate he is to get away and save himself from possible arrest and execution. This is the second of three predicted failures (Matthew 26:30–35). Unfortunately for Peter, the more he speaks, the more his Galilean accent reminds people of those who are closest to Jesus (Matthew 26:73).