John 18:15

When Christ was apprehended, the other evangelists tell us, all the disciples forsook him and fled; but it should seem that Peter, who all along the gospel history hath appeared more forward, and bold, and daring than any of the rest, came back; but who that other disciple was that went in with him, and in favour of whom Peter was admitted, we are not told. It is but a conjecture of those who think that it was John, for John was a Galilean as well as Peter, and would have been as much to be questioned upon that account as Peter was. They judge more probably who think it was the master of the house where Christ had ate the passover, and celebrated his supper; or some person of note in Jerusalem, who by reason of his reputation might have more free access to the chief magistrate than one of the apostles, who were but mean persons in the account of the Jews. This disciple, whoever he was, was one that had some familiarity and acquaintance with Caiaphas, which it is no way probable that either John or any of the apostles had.