“Then you will know the truth …” Christ says that those who have attained some knowledge of the truth will know it. It is true that those whom Christ was addressing were as yet untaught and had barely had their first lessons, so that it is not surprising if he promises them a fuller understanding of his teaching. But the statement is general. Whatever progress anyone has made in the Gospel, let him know that he needs to make further advances. The reward that Christ bestows on such perseverance is to make a man more familiar with himself. But by doing so, he merely adds another gift to the former, so that no one may think that he is paid anything by way of reward. For he who puts his Word in our hearts by his Spirit is the same who daily drives from our minds the clouds of ignorance which obscure the brightness of the Gospel. We should strive after the truth sincerely and earnestly, that it may be fully revealed to us. It is the same unvarying truth which Christ teaches his own from first to last; but first he enlightens them with small sparks, as it were, and finally pours out a full light upon them. Thus, until they have been fully strengthened, believers are in a sense ignorant about what they know. Yet this knowledge of faith is not so small and obscure that it is not efficacious for salvation.
“The truth will set you free.” Christ commends the knowledge of the Gospel from the fruit we receive from it, or, which is just the same, from its effect; namely, it restores us to freedom. This is an incomparable blessing. Hence it follows that there is nothing more excellent or desirable than the knowledge of the Gospel. All feel and acknowledge that slavery is a most wretched thing. Since the Gospel delivers us from this, it follows that the treasure of the blessed life comes from the Gospel.
We must now find out what kind of freedom Christ is describing here. It is that which sets us free from the tyranny of Satan, sin, and death. And if we obtain it by means of the Gospel, it is clear that by nature we are the slaves of sin. Next, we must find out the method of our deliverance, for so long as we are ruled by our own sense and nature, we are in bondage to sin. But when the Lord brings us to life by his Spirit he also makes us free, so that we are released from the snares of Satan and willingly obey righteousness. But new birth comes from faith. Hence it is evident that freedom comes from the Gospel.
We who are aware of our own slavery glory in no one other than Christ our Liberator. For the reason why we must regard the Gospel as having achieved our deliverance is that it offers and gives us Christ so we will be freed from the yoke of sin.
Lastly, we should observe that freedom has its degrees according to the measure of faith. This is why Paul, although already set free, still groaned and sighed for perfect freedom.
Calvin, J. (1994). John (Jn 8:32). Wheaton, IL: Crossway Books.