The Bible teaches that the Holy Spirit guides the believer:

However, when He, the Spirit of truth, has come, He will guide you into all truth; for He will not speak on His own authority, but whatever He hears He will speak; and He will tell you things to come (Jhn 16:13).

Now we have received, not the spirit of the world, but the Spirit who is from God, that we might know the things that have been freely given to us by God (1Cr 2:12).

Jesus promised the Holy Spirit would come and guide the believer into all truth. The work of the Holy Spirit illuminates the heart and mind of the believer to the things of Jesus Christ.

Spiritual Blindfold

The Bible reveals to us that Satan has put a spiritual blindfold over the minds of those who do not believe:

But even if our gospel is veiled, it is veiled to those who are perishing, whose minds the god of this age has blinded, who do not believe, lest the light of the gospel of the glory of Christ, who is the image of God, should shine on them (2Cr 4:3-4).

Once a person trusts Christ, the blindfold is removed and the Holy Spirit begins the work of illuminating the meaning of Scripture to his newly believing mind. This helps him better understand the things of God.