Paul is referring to the collection of money from the Corinthians for the believers in Jerusalem. AT: "who had encouraged your giving in the first place" (See: [[rc://en/ta/man/translate/figs-explicit]])
Titus was to help the Corinthians to complete the collection of money. AT: "to encourage you to finish collecting and giving your generous gift" (See: [[rc://en/ta/man/translate/figs-explicit]])