What is the religious ruling on a son who puts a sedative in his mother's tea to have intercourse with her while she is asleep?

Whoever commits this heinous act is a human being with a perverted nature and corrupt disposition. The seduction of Satan and the pursuit of desires have led him to the lowest levels of degradation and baseness of ambition. This is a matter that makes one's skin crawl and one's heart ache. The ruling for whoever commits this is execution, but the punishments must be carried out by the Sharia judge and by order of the ruler, after the punishment has been proven by evidence or confession.