What does 2 Corinthians 1:23 mean?

Prior verses made a grand, theological declaration. Paul has stated how all who affirm Christ as the "yes" to all of God's promises are established in Christ by God and anointed by God with His Holy Spirit. He has done so by way of defending himself against a charge of selfishly changing his travel plans to come and visit them. The implication is that a) his plans were changed, in part, by the leading of Christ and the Holy Spirit, and b) that he made the change in order to serve them better.

Now Paul gets to the heart of his motivation for delaying his return trip to Corinth from Macedonia. He calls on God to witness against him if he is not telling the truth—which coming from someone like Paul means he is undeniably telling the truth. He did not return from Macedonia to see them as he had apparently said that he would in order to spare them from something. The following chapter will reveal that he is sparing them from disciplinary action for potential sinfulness.