Now Paul describes the foundation; “built on the foundation of the apostles and prophets, Christ Jesus himself being the cornerstone” (2:20). To understand Paul’s message in this verse, we must pay careful attention to the little word “of”, meaning that the foundation of the apostles and prophets was Christ, not themselves. He further clarifies this point for us in 1 Corinthians 3; “For no one can lay a foundation other than that which is laid, which is Jesus Christ.” (3:11). Peter also refers to Christ as the “cornerstone” (1 Peter 2:7).
Without this truth and the person of Christ as the cornerstone of our gospel, we will have weak converts and they will foster weakness in the church. Paul took issue with anyone who did not preach the pure gospel (see Galatians 1:11-12; 2:4-5). What are you preaching?