What should one do who has a strong desire to marry but cannot do so, nor can he fast, and what is the ruling on one who commits zina (fornication/adultery) in this situation?

The fornicator must fear Allah and remember His punishment and what He has prepared for fornicators on the Day of Resurrection, including disgrace and humiliation, as the Prophet, peace and blessings be upon him, saw in the Hadith of the Oven, where he saw fornicators naked with flames coming to them.

We advise engaging in the pursuit of knowledge, associating with righteous people, eating less, staying away from temptations, and striving in work to facilitate marriage.

As for the ruling on the fornicator, the punishment in this world is stoning for the married (muhsan), and flogging and exile for the unmarried, followed by severe torment on the Day of Resurrection if he does not repent.