The passage
to which you refer says: "Now, brothers, I have applied these things to
myself and Apollos for your benefit, so that you may learn from us the meaning
of the saying, ‘Do not go beyond what is written.’" In context the
phrase "what is written" probably refers to whatever instructions
Paul has given them in this letter. You friend is wrong in his assertion
that there is "no context of Scripture," since obviously even if Paul
limits his words to the current letter, the current letter is itself Scripture.
On the other hand, I personally would not use this passage to defend sola
scriptura—there are better passages for that, including 2 Tim 3:16-17. (Eric D.
Svendsen, “Beyond
What is Written”)
