There isn't a clear statemen in the Quraan that explains stonning. However, Prophet Mohammed (PBUH) allowed and practiced this penalty back in the days.
The idea isn't in stoning. The idea is that you have been blessed with a wife (only those who are marreid get the stoning penalty) of choice, yet you choose to commit adultrey with another woman.
So the next big debate should be, the consequences of Adultrey against self and the society "beside getting stoned for it

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