What is the ruling on a man who commits adultery with a girl and her father refuses to marry her to him; should he marry her despite her father's refusal?

One must hasten to repent to Allah for zina (fornication/adultery), as it is among the gravest of major sins. Allah has coupled the threat of punishment for it with the threat of punishment for shirk (associating partners with Allah) and killing a soul, in His saying: {And those who do not invoke with Allah another deity or kill the soul which Allah has forbidden [to be killed], except by right, and do not commit unlawful sexual intercourse. And whoever does that will meet a penalty. The punishment will be doubled for him on the Day of Resurrection, and he will abide therein in humiliation.}

Its punishment in this world for an unmarried person is one hundred lashes and exile for one year, and for a married person, stoning, due to His (Allah's) saying: {The fornicating woman and the fornicating man, flog each one of them one hundred lashes}, and the Prophet's (peace be upon him) saying: "For the unmarried male and unmarried female, one hundred lashes and exile for one year, and for the married, stoning."

It has been mentioned in a prophetic vision that those who commit zina are tormented in Al-Barzakh (the intermediary realm between death and resurrection) in an oven, with flames reaching them from beneath.

For complete repentance, one must completely distance themselves from the girl involved and sever any relationship with her, even mere conversation, and then seek a chaste wife.