Read 1 Corinthians 1.
The basis of the redemptive message is the death, burial, and resurrection of Jesus Christ (1 Corinthians 15:1-4). It is personal faith in His sacrifice for one's sins against God that saves from eternal judgment and results in eternal life. Such forgiveness cannot be earned. It is a gift from God for simply believing in what the Bible calls the Gospel (good news).
In this chapter, the Apostle Paul uses at least four descriptive phrases for the Gospel.
1. "The word of the cross." (v.18a)
If there is no cross, there is no Gospel. That is how the full, final, once and for all payment for sin was mad. It is only through the substitutionary crucifixion of the Son of God that we have any good news concerning our being reconciled to God.
2."The power of God." (v.18b)
It is the same term in Romans 1:16. Humans are powerless to gain God's forgiveness and spiritual life. Salvation is an act of God. 1 Timothy 6:16 could not be more clear. Concerning Jesus, Paul wrote, "who alone has immortality." There is no alternative.
3. "The folly of what we preach." (v.21)
The Gospel message asks a person to believe in a God they cannot see nor figure out. By faith alone, one is called upon to commit their lives to Jesus and live with complete confidence in Him. This sounds absolutely foolish to those who view life as "seeing is believing" and who would rather trust their own reasoning over the word of God. The Scripture is consistent in its teaching that "believing is seeing."
4. "The wisdom of God." (v.24)
The wisest man who ever lived wrote, "There is a way that seems right to a man, but its end is the way to death." (Proverbs 14:12) When a human heart rejects the knowledge of God, it will turn to any and every false explanation. These false ways may salve the rebellious conscience for a time, but at the end of life there is no "good news." Only what the Bible calls the second death awaits them (Revelation 21:14-15) . "The fear of the LORD is the beginning of knowledge; fools despise wisdom and instruction." (Proverbs 1:7)
At the root of all rejection of God's word and the Gospel is the sin of pride. It is shear hubris for a person to think they know better than their Creator and the One who desires to be their Savior. Why has the Lord chosen such a plan that sets aside all human effort and depends solely on His grace? "...so that no human being might boast in the presence of God." And, "Let the one who boasts, boast in the Lord." At that point, our only response can be "Thank you, Jesus!"