How were the Corinthians to hear from Paul until he visited them?
Until Paul could visit Corinth again physically, the Corinthians were to be satisfied with hearing from him only by way of his letters. He wanted to come and see them, but in the interim, his written correspondence was the means by which they would receive his instruction and communication.
Les explains that Paul still wanted to come and see the Corinthians and stop in there again physically. However, until he could get there, they were going to have to be satisfied with hearing from him only by way of his letters. This shows Paul's continued care for them and the role of his written correspondence in teaching and guiding them before his planned visit.