We: the context here clearly indicates that the pronoun is exclusive. That is, it does not include the Corinthian Christians.
Commending ourselves: see comments on 3.1.
But: the conjunction used here is a rather strong one underlining the contrast between the denial of self-commendation and the affirmation that follows.
Giving you cause: the word translated cause has the basic meaning of “a starting point or base of operations for an expedition.” But it is used figuratively in the New Testament to indicate a basis or justification for doing something. Elsewhere it is translated “opportunity” in Revised Standard Version (Rom 7.8, 11; Gal 5.13). This may also be a good rendering here. Anchor Bible has “a suitable basis,” while Knox translates the whole clause “we are shewing you how to find material for boasting of us.”
To be proud of us: literally “boast of us.” The Greek suggests not simply inward pride but rather active “boasting.” While some good manuscripts read “of you” in place of of us, it is better to translate as in Revised Standard Version and Good News Translation.
Be able to answer: literally the word answer is not in the Greek text. The idea is not that of responding to questions, but rather to “have something to say [to those who are boasting]” (Anchor Bible, and similarly New American Bible).
Those who pride themselves in the context of this letter clearly refers to Paul’s opponents in Corinth (see 11.12). The root verb used here is the same as in the expression to be proud of us. Therefore the idea of outward boasting, rather than a mere inward feeling of pride, should be conveyed in translation. However, the context indicates that there are negative connotations involved here, while the previous reference is positive.
A man’s position and not on his heart: literally “in face and not in heart.” Since Paul seems to be speaking generally here and not exclusively of men, translators may wish to use inclusive language, such as in Revised English Bible (“whose pride is all in outward show and not in inward worth”) or New Revised Standard Version (“in outward appearance and not in the heart”). The Good News Translation translation “a man’s appearance” should not be understood as referring to a person’s physical appearance. The sense is that Paul’s opponents boast about external things such as their abilities and status (see 11.22-23).
The Contemporary English Version is a good model translation for the last part of this verse: “But we want you to be proud of us, when you are with those who are not sincere and brag about what others think of them.”
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 .