And so is literally “for,” carrying on the thought of verse 10 as a whole rather than stating the direct result of verse 10b.

Your before knowledge is strongly emphasized in the Greek text. One can translate this as “this knowledge of yours.”

This weak man may be expressed as “this Christian with small faith” or “this person who believes in Christ weakly.”

It is better to keep the phrase the brother for whom Christ died at the end of the verse, as in Revised Standard Version, in order to emphasize it. This phrase also stands as a new idea in this context. Die Bibel im heutigen Deutsch brings this point out by keeping the original order, but by dividing the sentence, making the second part “and yet he is your brother for whom Christ died.”

Brother means “fellow Christian,” as in 1.1 and many other places.

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 .