What did Paul ask Titus to do in 2 Corinthians 8:6?

Paul desired Titus to complete the grace already begun among the Corinthians, finishing the collection he had started. Titus picked up the mantle from Paul to gather offerings for the poor saints in person, ensuring the work of grace was brought to completion.

Les teaches that in verse 6 Paul desired Titus, who had begun the work, to finish in the Corinthians the same grace also. Titus was picking up the mantle from the Apostle Paul to gather offerings for the poor saints in person. This giving was not legal binding or according to a set of rules and regulations; the saints gave as God prospered them and as the Lord laid it on their heart. They first gave themselves to the Lord, stepping into God's saving grace, and then opened themselves to Paul and his ministry.

2 Corinthians 8:6

Insomuch that we desired Titus, that as he had begun, so he would also finish in you the same grace also.

What was Titus doing by picking up Paul's mantle?

Titus was continuing the Apostle Paul’s ministry by gathering offerings for the poor saints in person. Paul desired that Titus, who had already begun this work, would also finish in the Corinthians the same grace, completing the collection. Thus picking up Paul’s mantle meant carrying forward that apostolic task of collecting those offerings.