The Torah in Parashat Ahareh-Mot (Vayikra 18:7) commands, “Ervat Abicha…Lo Tegaleh” – that one may not “reveal his father’s nakedness,” a euphemism for intercourse with one’s father. A separate Biblical command, of course, forbids homosexual intercourse, which obviously would include an intimate relationship between a man and his father. The Torah added a separate command forbidding intercourse with one’s father, such that one who commits such an act is liable for two violations. Inserting even just the “Atara” (“crown”) of the organ transgresses this prohibition. This prohibition applies at all times and in all places. A person who intentionally transgressed this prohibition, in the presence of witnesses, is liable to Sekila (execution via stoning). One who transgressed this prohibition unintentionally is required to bring two sin-offerings – one for engaging in relations with his father, and a second for violating the prohibition against homosexual intercourse.