Negative Commandment #111
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
111. It is a negative commandment “do not uncover the nakedness of your father to have relations with him.”
As it states in Vayikra (Leviticus) 18:7, “the nakedness of your father... you shall not uncover.” This commandment is in addition to the general prohibition of a man having relations with another man. A person who transgresses this and has relations with his father: if there were witnesses and a warning given to them, both are given the death penalty of stoning. If there were no witnesses: if it was done intentionally, they are spiritually excommunicated. If it was done in error, he is obligated to bring two sin offerings (one for this sin and one for the general sin of having relations with another man.)
This applies in all places and at all times.