Reference for Makkot 27:12

ואידך איבעית אימא גמר עונש מאזהרה ואיבעית אימא נפקא ליה

And [as for where Rebbi Yitzchak derives the principle against deriving punishments] you can either say that he derives [the principle against deriving] punishment from [the principle against deriving] scriptural warnings, or you can say that he learns it out from

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