Albert Barnes Commentary 2 Corinthians 9:4

"lest by any means, if there come with me any of Macedonia and find you unprepared, we (that we say not, ye) should be put to shame in this confidence." — 2 Corinthians 9:4 (ASV)

Lest haply if they of Macedonia. This phrase refers to the possibility that if any of the Macedonians should happen to come with me and find that you had done nothing. He does not say that they would come with him, but it was by no means improbable that they would. It was customary for some members of the churches to travel with Paul from place to place, and interaction was constant between Macedonia and Achaia. Paul, therefore, had every reason to suppose that some of the Macedonians would accompany him when he went to Corinth. In any case, it was probable that the Macedonians would learn from some source whether or not the Corinthians were ready when Paul went to them.

Regarding the phrase We (that we say not, ye) should be ashamed, etc., Bloomfield says, "In this, one cannot help but recognize a most refined and delicate turn, inferior to none of the best classical writers." Paul had boasted confidently that the Corinthians would be ready with their collection. He had excited and stimulated the Macedonians by this consideration; he had induced them in this way to give liberally (2 Corinthians 8:1–4).

If it should now turn out, after all, that the Corinthians had given nothing, or had given sparingly, Paul's character would suffer. His truthfulness and his judgment would be called into question, and he would be accused of trick, artifice, and fraud in inducing them to give. Or, if he were not charged with dishonesty, he would still be humbled and mortified himself that he had made representations which had proved to be so unfounded.

But this was not all. The character of the Corinthians was also at stake. They had intended to make the collection. They had left the impression with Paul that it would be done. They had previously shown such a character as to make Paul confident that the collection would be made. If now this should fail by any means, their character would suffer, and they would have occasion to be ashamed that they had excited such confident expectations of what they would do.