Note 1 at 1 Cor. 16:5: Paul makes a very adamant statement that he is coming back to Corinth. Yet, at the writing of 2 Corinthians, which was nearly a year after this letter (see and Place of Writing in Introduction to 2 Corinthians), Paul still had not arrived at Corinth. In 2 Corinthians 1:16-2:10, Paul gives an explanation for this.

Paul purposely delayed his second trip to Corinth "to spare" them (2 Cor. 1:23). He did not want his visit with the Corinthians to be one where he was reproving them, so he delayed his trip, allowing them time to implement the changes he had prescribed in his letter we call 1 Corinthians (see Overview in Introduction to 1 Corinthians, p. 856). This is also his reason for writing what we call 2 Corinthians. He was still clearing up a few matters so that when he arrived, all would be well and his relationship with the Corinthians would be cordial instead of punitive.