In 1 Corinthians 3:11-15, Paul told the Corinthians that Jesus is the foundation and no one can add to the foundation. Also, Paul is telling the brethren that it is possible to build on the foundation. Brethren can build with different materials; i.e. gold, silver, precious stones, wood, hay, and straw.
The work that a man does becomes evident when it is tested with ﬁre. The work that is good will remain and the work that is bad will be destroyed. Paul also tells the Corinthians that if a man’s work is destroyed, he himself will be saved. This passage is talking about a man’s converts. In 1 Corinthians 9:1, Paul called the Corinthians his “work in the Lord.”
A man who converts people to Christ will more than likely see some of them fall away. Paul is encouraging the brethren to continue building on that foundation, but do not worry about losing your own salvation if those you convert fall away. John said in 3 John 4, “I have no greater joy than to hear that my children walk in the truth.” This is the way we should all feel, but realize that all who come to Christ (because of our “building”) will not remain because of weak faith.
In one of Jesus’ most well-known parables, the sower and his seed (Matthew 13), He taught that some who heard the word had no ﬁrm root because they had a temporary “faith.” When afﬂiction or persecution arose, they immediately fell away. It is unfortunate that so many do so, but Jesus and Paul both taught the sad reality of apostasy.