The earliest reference I could find is Christoph von Tiedemann on p. 42 of Persönliche Erinnerungen an den Fürsten Bismarck (S. Hirze, 1898, link) based on a 1897 talk:
"ich habe nicht schlafen können, ich habe die ganze Nacht gehaßt", sagte er mir eines Morgens
Von Tiedemann knew von Bismarck personally and spent a lot of time with him. The ...
Note that this answer was written before "Update 2" in the question appeared.
It seems to be an anecdote, reported only one single time, as "he once said", by one source, undated. It is of a singular nature, not repeating. In that single source it has no relation to any specific occasion and is even phrased with ambiguity, possibly even with an ...
Bismarck is very famous for his quotes, but even the Otto-von-Bismarck-Stiftung has no complete summary of them (at least online).
Asking them would be your best option for a reliable result, since his quotes are often used out of the original context.