That was the question that Phillip asked the Ethiopian eunuch as he sat in his chariot reading from the book of Isaiah (see Acts 8:26-40). The eunuch responded, "How can I, except some man should guide me?" He didn't know if the prophecy in Isaiah 53 was about the prophet himself, or some other man. He didn't have the spiritual understanding to see it was about Christ because he was yet to receive the Holy Spirit. He needed a spiritual man to show him Christ in the scriptures.
It is not my point in this post to expound the passage. I realize that it concerns the kingdom program of Israel. By the way, what was the eunuch reading that would make him ask about water baptism (v.36)? I believe the answer is found in Isaiah 52:15. I just want to draw an application in regard to understanding the Bible.
There are many people who read the Bible but do not understand it. How important is it to have understanding? It is a "wellspring of life unto him that hath it" (Prov. 16:22). We cannot "walk worthy of the Lord unto all pleasing, being fruitful in every good work, and increasing in the knowledge of God" without "spiritual understanding" (Col. 1:9-10).
Understanding comes from receiving the spiritual light of God's word (Ps. 119:130). We need the Spirit of God to illuminate our understanding to the spiritual truth of God's word. We cannot know the things of God without the Spirit of God (1 Cor. 2:6-16). The Bible is God's word, so we need Him to open our understanding to His truth (Lk. 24:45).
The first step to understanding the Bible is salvation. The Spirit of God dwells in every believer (Rom. 8:9). We are brought out of darkness into God's light the moment we believe the gospel (Acts 26:18; Eph. 5:8). Sadly, most are blinded to the gospel of the grace of God because they have only heard counterfeit gospels (2 Cor. 4:3-4; 11:4) that pervert the message by adding works (Gal. 1:6-12). They must hear the gospel light that Christ died for our sins, was buried, and rose again the third day (1 Cor. 15:3-4). We are saved by grace the moment we believe the gospel of Christ (Rom. 1:16).
The saved can still be in the dark when it comes to certain truth in the word of God. Traditions of men blind people to the truth of God's word. Paul prayed for believers to have the eyes of their understanding enlightened that they might know what is the hope of His calling (Eph. 1:15-18). Sadly, the majority of professing Christians today do not know the truth about our blessed hope (1 Thess. 4:13-18).
The Spirit of God will help us understand the word of God as we sincerely believe it, and study it His way (2 Tim. 2:15). We must depend upon the Spirit of God if we are going to be serious students of the scripture. As we believe and walk in the light that He gives us, He will give us more light. We must study the Bible in light of where we are living in God's plan of the ages. Christ raised up Paul to be the pattern and spokesman to the Body of Christ in this present age of grace. That is why he said, "Consider what I say; and the Lord give thee UNDERSTANDING in all things." (2 Tim. 2:7).