Corinthians 9:15

But I have used none of these things: neither have I written these things, that it should be so done unto me: for it were better for me to die, than that any man should make my glorying void (KJV)

Then: It was Paul's personal pride to be able to teach the gospel free of charge - in the same way that Christ taught it (Baker, p. 134). Henry describes it as a glory and a joy which he valued more highly than rights or even his life. All the while Paul writes he has in mind his next purpose. Similarly, Paul's readers should always be understanding his thought processes and looking forward to his next teaching point. In this case it is to come back to the teachings about eating meat offered to idols (Baker, p. 134).

Now: Today's believers and readers of the letter need to be as salient about Paul's teachings as the Corinthians eventually were .

Extra source: Cornerstone Biblical Commentary 1Corinthians (William Baker), 2 Corinthians (Ralph Martin & Carl Toney), ed. by Philip Comfort. Carol Stream: Tyndale House Publishers, c2006.
Commentary on the Whole Bible Acts to Revelation Vol VI by Matthew Henry online at http://www.ccel.org/ccel/henry/mhc6.iCor.x.html