Intertwined in the trial sequence (18:12–27) is the story of Peter’s threefold denial (18:15–18, 25–27; cf. Mark 14:66–72). Jesus has predicted Peter’s fear of identification in this crisis (John 13:36–38), and now it is fulfilled. John diverges, however, from the Synoptic story. He records that “another disciple” (likely John) who was acquainted with the priest let Peter into the courtyard (18:15–16). It is interesting that John records the specific type of fire (18:18). A charcoal fire (Greek anthrakia; NIV “fire”) will appear once again in 21:9, when Jesus reunites with Peter.
The Jewish interrogation is briefly recorded in 18:19–23, but…
Baker Publishing Group, The Baker Illustrated Bible Commentary, by Gary M. Burge