The content of 1 Corinthians does not seem to fit with what Paul says in verse 4, so the letter referred to here in verse 3 is apparently another letter, now lost, written between 1 and 2 Corinthians. In any case Paul is not referring to the present letter (2 Corinthians) but to a letter that he wrote earlier and which he refers to again in 7.8-12. Though no specific time is indicated, the letter was probably written only a few months earlier, not a few years earlier. Some interpreters regard 2 Cor 10–13 to have been part of the letter referred to in 2.3, but such a view is improbable (see “Translating 2 Corinthians” page 2).

To make clear that Paul is not talking about something that he wrote in chapter 1 of 2 Corinthians, Good News Translation adds “that letter.” In some languages it may be necessary to say “another letter” or “that other letter.”

I wrote as I did: Good News Translation adds the word “to you” (also Bible en français courant, Parola Del Signore: La Bibbia in Lingua Corrente, Biblia Dios Habla Hoy), since the context clearly indicates that the letter was written to the Corinthians.

The words so that when I came should not be misunderstood to mean that Paul is here referring to a visit that he had already made. He has not yet visited Corinth again since he wrote the letter mentioned in this verse, so the words so that when I came refer to a visit that he planned to make as soon as possible, and that he still plans to make. Translators may consider saying “the reason that I wrote was so that when I do visit you again…,” or else follow the simple form of Good News Translation.

On pain see comment on verse 2.1.

From those who should have made me rejoice: an indirect reference to the Corinthian Christians. Some possible models for this part of the verse are “I did not want to be made sad by the very people who would have made me happy” or, more directly, “I did not want to visit you, because meeting with you would only make me unhappy. And you are the people who should make me happy.”

That my joy would be the joy of you all: this clause tells the reason for Paul’s wanting to be happy. In some languages it may be better to transpose this to the beginning of the verse, as is done in Contemporary English Version: “The reason I want to be happy is to make you happy.” Nearly all interpreters understand this to mean, as in Good News Translation, that when Paul was happy, then all of the Corinthians would be happy too. It is possible, though less likely, that the sense is the following: I will be happy when you are all happy.

Knox captures the meaning of the verse as a whole, translating as follows:
• And those were the very terms in which I wrote to you: I would not come, if it meant finding fresh cause for sorrow where I might have expected to find cause for happiness. I felt confidence in you all, I knew that what made me happy would make you happy too.

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 .