A common translation of the Latin hortative memento mori is "Remember thou shalt die."
I am not interested in a discussion of the Latin, nor of what the expression actually means in English. I am more interested in why English speakers chose the formulation "Remember thou shalt die" over "Remember thou wilt die," considering the implications of "shall" and "will" in English.
This thoroughly correct answer to a similar question definitely implies that "will" would be the right choice. –And yet Google has almost three thousand results for "Remember thou shalt die" (in quotes), and a mere two for "Remember thou wilt die."
Can anyone explain why this is? And: Which form is correct?
Related: The use of "will" in assumptions
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N.B.: Mentions of "will" in this question refer to the future auxiliary, not to the verb "to will." Separately: I am not interested in answers which assert that "shall" and "will" are practically interchangeable these days.
Best Answer
In Shakespeare, shall and will were not used according to the "traditional rule in Standard British English" described in your link. You can see from this Ngram that there was a big change in the rules for shall and will between 1600 and 1700, at least for first person. Since the comments say this line was composed around 1600, the grammar would presumably be that of Shakespeare.
As far as I can tell from looking at examples in Shakespeare, for people he used will to indicate volition on the part of the actor, and shall to indicate lack of volition. Thus, thou shalt die means you are dying without necessarily wanting to.
EDIT: I have found a reference for this usage. From The Cambridge History of the English Language: