We have known this for a long time. No need to read minds.
If you're talking about something like a citation guideline (and not something else, like "we have known the full verse of Matthew 11:11 for a long time"), well, it's not written anywhere obvious, such as the Religion Moderator profile or some other "official" page. Although I can't claim to have read everything, I've also never seen such a rule invoked elsewhere on this forum.
(Heh, even before I read your post I was having some new thoughts about sola scriptura, thanks to what I was already thinking about what is "written." Although these thoughts are not yet formed enough to post here--and in my mind they could be sufficiently on-topic to fit--I do notice how trains of thought can start from relatively little things.)