What is the advice of the Sharia to a young man who embraced Islam after committing fornication with a Christian woman who became pregnant by him, and she threatened him with a rape lawsuit if he does not marry her? Should he marry her while she does not believe in the prophethood of Muhammad (peace be upon him), and what is the ruling on the lineage of the coming child?

Firstly: Islam eradicates the sins that preceded it.

Secondly: It is permissible for your friend to marry the Christian woman, provided she repents from fornication and is characterized by chastity; due to the Almighty's saying: (And [lawful in marriage are] the chaste women from among the believers and the chaste women from among those who were given the Scripture before you, when you have given them their due bridal money, desiring chastity, not [desiring] illicit intercourse or taking [secret] lovers).

Thirdly: If a woman becomes pregnant from fornication, the child is not attributed to the fornicator according to the majority of scholars. Many of them hold the view that the marriage contract is not permissible until she gives birth. Some scholars, including Shaykh al-Islam Ibn Taymiyyah, were of the opinion that the child is attributed to the fornicator if the woman was not legally married to anyone else.