How do we know that the gospel is a mystery that needs revelation?

The mystery of the gospel is highlighted in 1 Corinthians 2:7-10, where Paul asserts that the wisdom of God, which includes the gospel, is hidden from the wise and is revealed to those whom God has chosen. This means that apart from divine revelation, individuals cannot understand or accept the truths contained in the gospel. It is only through the Holy Spirit's work that the mystery is unveiled, allowing the hearts of sinners to comprehend their need for Christ and the fullness of salvation he provides. Thus, the gospel's revelation is a testament to God’s sovereign grace.