Negative Commandment #120
Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos)
By the Chofetz Chaim
This book lists the Torah mitzvos that can be observed today
Second Section – the Negative Commandments
120. It is a negative commandment “do not have relations with one’s daughter, even if she was born from illicit relations, as she is still his daughter”
This negative commandment does not appear explicitly written in the Torah, but it is learned through a kal v’chomer (if one thing is true, then something else must certainly be true) and a gezerah shava (learned by comparing words). The punishment for this sin is death by burning. If it was done intentionally but without warning, the punishment is spiritual excommunication. If it was done in error, a sin offering is to be brought. If it is his daughter from his wife, he is punished twice (one because it is his daughter and one because of the law of not having relations with a mother and her daughter - Vayikra (Leviticus) 18:17).
This applies in all places and at all times.