Expositor's Bible Commentary Commentary John 18:15

"And Simon Peter followed Jesus, and [so did] another disciple. Now that disciple was known unto the high priest, and entered in with Jesus into the court of the high priest;" — John 18:15 (ASV)

Peter and an unnamed disciple (possibly John, cf. 13:23–24; 20:2–3) had traced Jesus and his captors back from Gethsemane over the Kidron Valley to the residence of the high priest in Jerusalem. This anonymous disciple was known to the household of the high priest and readily obtained access for himself and Peter; there is evidence that John may have been distantly related to that family. Peter was in the “courtyard,” standing with servants and retainers by a fire (v.18).