This is why: or, more literally, “For this [purpose].” Many modern versions such as Good News Translation recast the sentence and use “because” later in the sentence.

I wrote refers to the letter mentioned in 2.3. As in 2.3, Good News Translation adds the object “to you.” Since Paul is referring to a specific letter, Good News Translation also adds “that letter.”

That I might test you and know: literally “in order that I might know the value [or, worth] of you.” The term used here has to do with the proven value of something as a result of a testing process. Another rendering can be “so that I may know your true character.” The “test” was to determine whether they were truly committed to Paul and to his apostolic teachings.

Paul does not state the person to whom the Corinthians are to be obedient. Most probably Paul was referring to their obedience to his instructions (so Good News Translation) or to his authority (so Revised English Bible). The implied contrast to their obedience to Paul’s authority is probably not that they were self-willed, but rather that they were obedient to others who were opposed to Paul.

The pronouns you in verses 9 and 10 are plural, again referring to the Corinthian Christians.

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 .