john 17:12 While I was with them in the world, I kept them in thy name: those that thou gavest me I have kept, and none of them is lost, but the son of perdition; that the scripture might be fulfilled. - Free Bible Online

      12. I kept--guarded.
      them in thy name--acting as Thy Representative on earth.
      none of them is lost, but the son of perdition--It is not implied here that the son of perdition was one of those whom the Father had given to the Son, but rather the contrary (Joh 13:18) [WEBSTER and WILKINSON]. It is just as in Lu 4:26, 27, where we are not to suppose that the woman of Sarepta (in Sidon) was one of the widows of Israel, nor Naaman the Syrian one of the lepers in Israel, though the language--the same as here--might seem to express it.
      son of perdition--doomed to it (2Th 2:3; Mr 14:21).

JFB.