So: this represents the conjunction often translated “Therefore” (New Revised Standard Version). It introduces the logical conclusion of Paul’s argument on this point.

Give proof … of our boasting: the sense is “give proof of the truthfulness of our boasting.” Good News Translation expresses this sense with “show” and by adding the words “will be sure of it and know that we are right.”

Our boasting about you: different forms of the word “boast” appear nearly thirty times in this letter. The references are sometimes positive (as in this case) and sometimes negative. In this context translators may say something like Contemporary English Version‘s “why we bragged about you,” or possibly “the expression of our happiness with you.” See also 1.12.

Before the churches is literally “in the face of the churches.” Paul wants Christians in other churches to see or be made aware of the love that the Corinthians have. The churches may refer to all the local assemblies. Good News Translation inserts the word “all” (so also New Jerusalem Bible and Martin). Perhaps, though, Paul is referring only to the churches that are mentioned in verses 19 and 23, that is, the churches which appointed these men to represent them. So Nueva Biblia Española says “before their churches.” In view of the difference of opinion among scholars on the meaning of churches here, it is probably better not to add the word “all” as Good News Translation has done.

As in 8.8, the Greek does not specify the object of your love. Good News Translation says “your love to them [Titus and the brothers],” but this could be either their love for Titus and the brothers, which some translations make explicit (Bible en français courant, Biblia Dios Habla Hoy, Nova Tradução na Linguagem de Hoje), or their love for Paul. In light of 8.7, it is unlikely that this refers to Christian love in general.

Quoted with permission from Omanson, Roger L. and Ellingworth, Paul. A Handbook on Paul’s Second Letter to the Corinthians. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .