What is the punishment in Islam for a fornicator who commits adultery with his father's wife, if he is not muhsan (meaning, not a married person)? Is it execution or 100 lashes?

The majority of scholars agree that the punishment for someone who commits adultery with a mahram relative—whether it be his father's wife or another—is the same as the punishment for someone who commits adultery with an unrelated woman. This is one hundred lashes for the unmarried and stoning for the married. However, another group stated that he should be killed unconditionally, citing the hadith, "Whoever has intercourse with a mahram relative, kill him." But the more authoritative view is that of the majority, because the hadith is weak and does not specify the generality of the verse.