‘For we are not as the many, corrupting (or ‘peddling') the word of God, but as of sincerity. But as of God, in the sight of God, speak we in Christ.'
So, Paul concludes, they should now be able to see the truth about him and his fellow-workers. They are not, like many, corrupting and misinterpreting the word of God, or alternately hawking it about and peddling it for money. Those who did such things were people who claimed to be ‘sufficient' but were not. Rather Paul and his fellow-workers are ‘of sincerity'. They are genuine and true in their presentation of the word of God. They have no desire for worldly gain. Indeed they are revealed to be ‘of God', following in His triumphal train, and successfully wafting His truth to many. And it is because they are ‘of God' that, in His very presence and before His very eyes, they speak in Christ.
And having now been caught up in his theme, and in his gratitude to God, he continues it on, only coming back to his narrative in 2 Corinthians 7:5.