Bhagavad Gita, Chapter 17, Verse 1

Arjuna said: Those who setting aside the ordinance of the Shâstra, perform sacrifice with Shraddhâ, what is their condition, O Krishna? Is it Sattva, Rajas or Tamas?

A real, honest question follows directly from the previous chapter's warning, what about faith without the rulebook.

Arjun doesn't let Krishna's scripture-authority instruction go unquestioned, he asks about a real, common case, sincere worship that skips the guidelines. That question opens this whole chapter.