‘Jesus therefore said to those Judaisers who had believed in him, “If you dwell in my word then are you my disciples indeed, and you will know the truth and the truth will make you free”.'
Jesus then spoke a word to some of the Judaisers who had showed some response to Him, ‘If you persevere in and meditate on my teaching, you are truly my disciples, and you will know the truth, and the truth will make you free'. It was a glorious promise of hope. The truth was now open to them, and if they will but know and receive that truth it will make them truly free. But there is only one test of true faith and that is perseverance and continuance. By such perseverance those who receive His teaching (‘word') will come into a fuller understanding of truth, especially the truth about Him, and will thus find freedom from sin and its power. And then they will find true freedom, not the freedom from the tyranny of Rome which they have previously longed for, but a greater freedom, a freedom from the tyranny of that greatest despot of all, sin.
So even though some of the Judaisers have made some kind of response of faith towards accepting Him as from God, Jesus cannot rest satisfied until that faith is deeply rooted in the truth about Him, a truth that is in fact found in Himself (John 14:6).
There is an important lesson here. The only final basis of assurance of salvation for anyone is continuance in responding to the truth. A ‘saved' man can backslide, but he can have no assurance while in his backsliding, and, if it is permanent, abundant Scriptures testify to the fact that it indicates that he was not really saved. When the Saviour saves it is effective, even though there may be the occasional blip. He does not fail in His work.