What is the ruling on adultery (zina), and what is its ruling after marriage, and what is the ruling on the child born of adultery after marriage?

Allaah has forbidden zina (fornication/adultery) and has forbidden the means that lead to it. He says: (And come not near to unlawful sex. Verily, it is a Fâhishah [a great sin, an illegal sexual intercourse] and an evil way that leads to hell unless Allaah forgives him]” [al-Isra’ 17:32]. And He commanded to lower the gaze and to guard one's chastity. The punishment for the never-married fornicator is one hundred lashes and exile for one year. As for the married adulterer, his punishment is stoning to death. The jurists differed as to whether it is limited to stoning only or if he is lashed then stoned. As for the fetus resulting from zina, it is forbidden to abort it. If it is born alive, it is not attributed to its biological father from zina, and there is no inheritance between them. Rather, it is attributed to its mother, and it inherits from her, and she inherits from it.