Gospel: that is, the Good News about Jesus Christ.

In lands beyond you probably refers to new territory to the west, as far as Spain (see Rom 15.24, 28). The word translated lands beyond is a noun created from an adverb meaning “beyond.” It is used only here in all the New Testament. Some versions supply the noun “lands” (Revised English Bible as well as Revised Standard Version), others have “regions” (New International Version) or “areas” (Barrett). There is no particular focus on political entities, as Good News Translation might suggest. So it is probably better to use a more general geographical term such as “regions.” Since Spain is to the west of Corinth, it can be legitimate to translate “in areas to the west of you.”

Without boasting of work already done in another’s field repeats the thought of verse 15a. Some may prefer to translate this as a separate sentence: “[By going into places where no one has preached the Good News] we will not praise ourselves for work that other people have already done in those places where God gave them work to do.”

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 .