Albert Barnes Commentary 2 Corinthians 8:19

"and not only so, but who was also appointed by the churches to travel with us in [the matter of] this grace, which is ministered by us to the glory of the Lord, and [to show] our readiness:" — 2 Corinthians 8:19 (ASV)

And not that only. Not only is he esteemed on account of other services which he has rendered through his preaching and writings, but he has also received a new mark of the churches' confidence in being appointed to convey the collection to Jerusalem.

Chosen of the churches. Chosen by the churches. Many agreed with the choice, showing that they had entire confidence in him. Paul had been unwilling to have charge of this contribution alone (1 Corinthians 16:3–4; compare to 2 Corinthians 8:20), and he had arranged for someone to be appointed to undertake it. He probably expected that the church at Corinth would also agree to this appointment.

With this grace. The marginal note says "gift." (See 2 Corinthians 8:1). The word here refers to the alms, or the collection that had been made.

Which is administered by us. That is, which is undertaken by us. Paul had been instrumental in arranging this collection.

To the glory of the same Lord. The Lord of us all. The purpose was to promote the glory of the Lord by showing the influence of religion in producing true benevolence.

And declaration of your ready mind. That is, to give you an opportunity to demonstrate your readiness to do good to others and to promote their welfare.