Those Who Believe Will Understand the Truth

"We are of God: he that knoweth God heareth us; he that is not of God heareth not us. Hereby know we the spirit of truth, and the spirit of error." (1 John 4: 6)

Whenever we read the word "truth" in the Bible, we must think of the Gospel, not just statements about exists or what is real, versus what is not real or what is made  up:

"To whom we gave place by subjection, no, not for an hour; that the truth of the gospel might continue with you." (Galatians 2: 5)

and then

"But when I saw that they walked not uprightly according to the truth of the gospel, I said unto Peter before them all, If thou, being a Jew, livest after the manner of Gentiles, and not as do the Jews, why compellest thou the Gentiles to live as do the Jews?" (Galatians 2: 14)

If these statements have not renewed a person's mind, there is more:

"In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise," (Ephesians 1: 13)

"For the hope which is laid up for you in heaven, whereof ye heard before in the word of the truth of the gospel;" (Colossians 1: 5)

The Gospel is all about the grace of God, in that we are justified before God because of Jesus:

"37But he, whom God raised again, saw no corruption. 38Be it known unto you therefore, men and brethren, that through this man is preached unto you the forgiveness of sins: 39And by him all that believe are justified from all things, from which ye could not be justified by the law of Moses." (Acts 13: 37-39)

The law does not justify, but kills and condemns:

"But if the ministration of death, written and engraven in stones, was glorious, so that the children of Israel could not stedfastly behold the face of Moses for the glory of his countenance; which glory was to be done away:" (2 Corinthians 3: 7)

and then

"9For if the ministration of condemnation be glory, much more doth the ministration of righteousness exceed in glory" (2 Corinthians 3: 9)

In Christ, we are justified, made righteous in His righteousness.

This is the spirit of truth, and the same Holy Spirit which grants us sonship (Romans 8: 15) convicts us of righteousness (John 16: 11)

Truth is not about what you know, or even who you know, but He who has been from the beginning (1 John 2: 14), that He knows you (Galatians 4: 6) and sees you in His Son Jesus.

Anyone who does not walk by the faith of the Gospel, that we are saved by grace through faith, taken from dead in trespasses to alive in Christ: will not understand the grace of God, and will not understand what you say to them.