Am 18.08.2017 um 14:43 schrieb mayqel qunenoS:

As soon as he finishes his speech/passage, another person wants to ask him "how do you know it (this fact) ?

Would it be correct for him to say {chay' DaSov ?} And by the use of the prefix {Da-} the {Sov} having as an elided object the entire preceding speech/passage ?

Good question. I have three answers to this, with grades of correctness.

a) I would accept {chay' DaSov} with no objection, but I have no evidence this is correct.

b) Taken the book, there is a way to refer to a previous sentence, maybe {chay' 'e' DaSov}, but this maybe wrong.

c) To be on a very clean grammatical track, I would suggest to say what you even used in your question:
  {chay' ngoDvetlh DaSov?}
  "How do you know that fact?"

I find myself preferring chay' bISov?

-- 
SuStel
http://trimboli.name