For is omitted in some Greek manuscripts and is printed in square brackets in the UBS Greek text. Whether Paul wrote this word or not is unimportant. The connection with verse 13 is clear, and translators must decide for themselves whether a connecting word such as For is natural in their own language.

The question arises whether I here means strictly Paul alone, or whether Paul is using himself as an example. The same problem arises in chapter 13 (see the introduction) and in Romans 7. Most translations have “I,” like Revised Standard Version and Good News Bible. Die Bibel im heutigen Deutsch, however, brings out the meaning that Paul is using himself as an example by translating “When someone … speaks” in verse 13, and using “he” in verse 14 (but not verse 15). This is possible, but it is important to keep the contrast between “I” in verse 15 and “you” in verse 16.

In a tongue may be rendered as “in strange sounds” or “in ecstatic speech” (see verse 13 and elsewhere in this chapter).

Mind here refers to a person’s thinking apparatus or intellectual faculty, which is an integral part of human nature.

The spirit, on the other hand, is breathed into man by God (see Gen 2.7, which Paul quotes in 15.45). It is my spirit, but this does not mean here just one part or aspect of human nature; it is the human spirit acting under the inspiration of the Holy Spirit. Die Bibel im heutigen Deutsch brings this out by translating here “when (anyone) speaks in such languages, the Holy Spirit prays in him…,” and in verse 16, “but when you praise God in the language of the Spirit….” This is possible, though New International Version translates “your spirit” in verse 16.

Is unfruitful probably means “receives no benefit from.”

Quoted with permission from Ellingworth, Paul and Hatton, Howard A. A Handbook on Paul’s First Letter to the Corinthians, 2nd edition. (UBS Handbook Series). New York: UBS, 1985/1994. For this and other handbooks for translators see here .