Here is your OP,
>>Whenever the three days and three nights of Matthew 12:40 is brought up in a "discussion" with 6th day crucifixion folks, they frequently argue that it is a Jewish idiom for counting any part of a day as a whole day. I wonder if anyone has documentation that shows that the phrase "x" days and "x"nights was ever used in the first century or before when it didn’t include at least parts of the "x" days and at least parts of the "x" nights?<<
I am - for one - too simple a man to understand what you say; it's not SIMPLE enough for me. First.
Next, WHAT, is the TRUTH which you want to explain or establish or confirm?
That 'the phrase "x" days and "x"nights was in fact used in the first century or before', but did 'not include' any parts of the "x" days' or 'at least parts of the "x" nights'?
Please forgive me, but I cannot make head or tail of what you mean.
I can at best guess that you meant, Was the phrase from Matthew 12 and Jonas 2, "three days and three nights" used in Christian documents in the first century or before?
And the answer is of course, yes! In Matthew 12:40 and Jonas 1:17.
Last, So I gave you the New Testament passages that exactly define and make clear which those "three days and three nights" that comprised the "three days" OF THE WEEK to which Jesus referred, HISTORICALLY, were. the Fifth, Sixth and Seventh Days-of-the-week.
Clarity and simplicity, dear Strats. Just simplicity and clarity ... as Schmidt said in which TRUTH expresses itself. May I add, simplicity, clarity and tolerance or patience towards the simpleminded like me.