With his first image, Paul emphasized the humble position of a preacher. With his second image, he emphasizes the special nature of the preacher’s work and the great responsibility that comes with it.
Paul reminds the Corinthians of his own role in their history. He is the one who laid the foundation
when he preached and taught them the gospel for the first time. The task of laying the church’s foundation had been given specifically to the apostles (Ephesians 2:20). It was by the grace of God
that Paul had become an apostle (see also Ephesians 3:7) and that he was able to do his work properly, like a skilled master builder.
Without mentioning names, Paul issues a warning to other preachers to take care how they build on the foundation that was laid by him.
10 Selon la grâce de Dieu qui m'a été donnée, j'ai posé le fondement comme un sage architecte, et un autre bâtit dessus. Mais que chacun prenne garde à la manière dont il bâtit dessus.