For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men who suppress the truth in unrighteousness, because that which is known about God is evident within them; for God made it evident to them." (Romans 1:18,19)
Will God judge those guilty who have never heard the gospel of Jesus Christ? Although it may initially seem unfair, the answer is "yes". First, we need to understand that people will spend eternity in hell not just because they have rejected the salvation offered in Christ Jesus, but because the penalty for sin is death and everyone sins; "...as it is written, 'There is none righteous, not even one; there is none who understands, there is none who seeks for God.'" (Romans 3:10,11).
But what about those who have never read a Bible and have never heard any of God's commandments? Romans 1:18 and19 tells us that we are born with a conscience that knows right from wrong. Furthermore, God has revealed Himself in His creation; "For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse." (Romans 1:20).
But what about babies and those who are mentally retarded. Will God also judge them guilty for their sins? There seems to be some indication in the Bible that those who have not reached some mental age of accountability are forgiven for their sins in Christ. When King David's infant son born by Bathsheba died, David said; "But now he has died; why should I fast? Can I bring him back again? I will go to him, but he will not return to me." (2 Samuel 12:23).
The Bible doesn't give us much more information about the eternal fate of those who die before reaching the age of accountability. I wonder if this remains a mystery because sinful parents might kill their children fearing that their child might reach the age of accountability and then reject the gospel. Other parents would live in constant fear believing that their child could die before hearing and believing the gospel of salvation. This we do know-- God is just and that everything He does is good and perfect, including all of His judgments. We can also be comforted by Jesus' expressed love for children; "But Jesus said, 'Let the children alone, and do not hinder them from coming to Me; for the kingdom of heaven belongs to such as these.'" (Matthew 19:14)
No one should, however, doubt that God will punish the guilty and that there will be greater punishment in hell for those who have heard the gospel, but have rejected it; "For if we go on sinning willfully after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, but a terrifying expectation of judgment and the fury of a fire which will consume the adversaries. Anyone who has set aside the Law of Moses dies without mercy on the testimony of two or three witnesses, How much severer punishment do you think he will deserve who has trampled under foot the Son of God, and has regarded as unclean the blood of the covenant by which he was sanctified, and has insulted the Spirit if grace?" (Hebrews 10:26-29)
It is good, I think, to end this commentary about guilt on a positive truth from Hebrews 10:39; "But we are not of those who shrink back to destruction, but of those who have faith to the preserving of the soul." Maranatha!