Jamieson, Fausset and Brown on John 8:31-33

31-33. Then said Jesus to those Jews who believed, If ye continue in my word, then are ye my disciples indeed, &c.--The impression produced by the last words of our Lord may have become visible by some decisive movement, and here He takes advantage of it to press on them "continuance" in the faith, since then only were they His real disciples (compare Joh 15:3-8), and then should they experimentally "know the truth," and "by the truth be made (spiritually) free."