Is it permissible for a Muslim to have sex, even once, knowing that this act is forbidden?

Allah has forbidden zina (unlawful sexual intercourse) and has equated it with shirk (polytheism) and taking a life. He described it as an abomination (fahishah) and prohibited approaching it. He commanded believers to lower their gaze and guard their private parts. Whoever commits this sin must repent to Allah and hasten to marry. If unable to do so, he must fast. He should also associate with righteous and pious people and avoid bad companions.