How do we know only some benefit from the gospel?

Scripture teaches us that the gospel, while powerful, does not benefit everyone uniformly. Hebrews 4:2 articulates that the word preached did not profit those who heard it because they did not mix it with faith. This highlights the necessity of divine faith given by God for the gospel to have a saving effect. Consequently, the distinction is made between those who respond in faith due to God's grace and those who heed the message without true belief or understanding, ultimately leading to condemnation rather than salvation.