Note 1 at 1Co 16:5: Paul made a very adamant statement that he was coming back to Corinth. Yet, at the writing of 2 Corinthians, which was nearly a year after this letter (see Life for Today Study Bible Notes, Introduction to 2 Corinthians, Date and Place of Writing), Paul still had not arrived at Corinth. In 2Co 1:16-2:10, Paul gave an explanation for this.

Paul purposely delayed his second trip to Corinth "to spare" them (2Co 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 Life for Today study Bible Notes, Introduction to 1 Corinthians). 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.