He was speaking of Judas, the son of Simon Iscariot; for Judas, one of the Twelve, was going to betray him.
In context
69and we have believed, and we have come to know, that you are the Holy One of God.” 70Jesus answered them, “Did I not choose you, the Twelve? And one of you is a devil.” 71He was speaking of Judas, the son of Simon Iscariot; for Judas, one of the Twelve, was going to betray him.