Let's say I read a commentary on a work by Tolkien (say, The Hobbit) which points out a particular theme/way to read the book. Let's say I forget that the commentary applied to The Hobbit and end up reading The Lord of the Rings through that lens. Then let's say I do some scholarly writing on the work using the insights I got from reading through the commentary's lens. Would I need to mention in some way that I obtained my insights by an accidental misapplication of that commentary? Also, let's say that because of reading that commentary, I become super-sensitive to a certain theme and it dramatically alters the way I read anything at all. Would I need to mention said commentary in scholarly work, even though it applied to The Hobbit and I might be writing on that theme in an unrelated work (say, Sundiata)? Thanks!
You need the citation if you are quoting or citing specifics from the commentary. I would not think you need a citation for everything you've ever learned, so if you learned something from the commentary, and you are applying it to a different piece, it depends entirely on how specific your reference is.
In a scholarly work, cite all references. This includes direct quotations, paraphrasing, arguments or conclusions presented in other scholarly works, etc.
