Makkot 14 - No Double Punishment for the Same Offense
Normally, two punishments cannot be administered for one transgression, because one is punished " corresponding to his wickedness ," but not more. However, Rabbi Yishmael allows both lashes and death penalty, because it is all "one long death."
Rabbi Yitzchak says that for relations with his sister one is cut off, but does not get lashes. Talking about the laws of incest, the Torah repeated the prohibition of one's sister . There is a rule, "Exception proves the rule." In our case, when incest with one's sister is prohibited yet again, on the pain of being cut off, this teaches that being cut off is the only punishment for it, and one does not get lashes. It then also teaches that one does not get lashes for all other similar transgressions.
The Sages, who don't agree with Rabbi Yitzchak, say that the Torah here speaks about someone who fathered two girls with his mother, then a son with one of the girls, and his son then had relations with the other girl, who is the now his sister, father's sister, and mother's sister - such a person gets three sets of lashes.
Art: John Singer Sargent - The Daughters Of Edward Darley Boit