It is by a knowledge of the truth that men are saved.
Observe that stress is laid upon the article: it is the truth, and not every truth. Though it is a good thing to know the truth about anything, and we ought not to be satisfied to take up with a falsehood upon any point, yet it is not every truth that will save us. We are not saved by knowing any one theological truth we may choose to think of, for there are some theological truths which are comparatively of inferior value. They are not vital or essential, and a man may know them, and yet may not be saved. It is the truth which saves. Jesus Christ is the truth: the whole testimony of God about Christ is the truth. The work of the Holy Ghost in the heart is to work in us the truth. The knowledge of the truth is a large knowledge. It is not always so at the first: it may begin with but a little knowledge, but it is a large knowledge when it is further developed, and the soul is fully instructed in the whole range of the truth.
“God our Savior; who will have all men to be saved, and to come unto the knowledge of the truth.”—1 Timothy 2:3-4
Excerpt from sermon “Salvation by Knowing the Truth” by C. H. Spurgeon