What does 2 Corinthians 11:31 mean?

To counter false teachers, Paul sarcastically "boasts" about his Christian service, a description that mostly entails the hardships he has survived. He may have sensed that the list of ways he has suffered for Christ sounds like a lot. Maybe he wonders if some of his readers will doubt him. He is aware, also, that what he is about to describe in the following chapter may even be more difficult to believe. He finds it necessary here to insist that he is not lying, staking his claim to truthfulness on God Himself.

He writes that the God and Father of Jesus, who is Lord and is blessed forever, knows that Paul is not lying either about what he has said or about what he is about to say. Claiming God as his literal witness is the highest form of assurance Paul can give to his readers that he is telling the truth.