What does 2 Corinthians 8:5 mean?

This portion of 2 Corinthians describes evidence that the churches in Macedonia have received God's grace. Despite their own poverty and suffering, they begged to be included in giving aid to suffering Christians in Jerusalem. Once included, they gave generously, even beyond their means. Paul and the others administering the collection had not expected this. Paul now says that it revealed that the churches in Macedonia had given themselves to the Lord and then, by God's will, had given themselves also to Paul.

The Corinthians had previously committed to being included in Paul's collection for those in Jerusalem, as well, and Paul had given them instructions for how to raise the funds (1 Corinthians 16:1–6). Paul may have wondered if his strained relationship with them would cause them not to follow through on this commitment. Now that he has received the report from Titus, though, about their renewed longing for him (2 Corinthians 7:7), he will ask them to follow the example of the Macedonians and give themselves first to the Lord and then to him.