1 Corinthians 3:11

For other foundation can no man lay than that is laid, which is Jesus Christ (KJV)

Then: Any other worker who comes to Corinth can not lay down another foundation, for the foundation is Christ. The new workers have tasks, but it is not to change the foundation. That job was done and done well (Baker, p. 57).

Now: We define the foundation, the gospel, the good news of Christ. He is the Son of God. He came to us through God's love and taught us that "We love, because he first loved us." Because Christ took the punishment for all our sins, was crucified for them, we are forgiven. Because in God's plan, he conquered death by being resurrected from the dead, we will be resurrected. Christ led the way to eternal life, and all who believe in him will also be resurrected into the eternal presence of the Lord. We have the promise of John 3:16, "For God so loved the world that he gave his only begotten Son, that whosoever believeth in him should not perish but have everlasting life." There is no other truth and there is no other foundation. Men cannot change the word of God.

Extra Source: Cornerstone Biblical Commentary 1 Corinthians (William Baker), 2 Corinthians (Ralph Martin & Carl Toney), ed. by Philip Comfort. Carol Stream: Tyndale House Publishers, c2006.