The Prayer of the Fornicator

Question :

Is the prayer of the fornicator invalidated, bearing in mind that I am unable to marry, due to my financial circumstances?

Answer:

Allah, Most High says:
"And come not near to unlawful sex. Verily, it is a Fähishah (i.e. anything that transgresses its limits: a great sin), and an evil way (that leads one to Hell unless Allah forgives him)."

And the scholars have unanimously agreed that illegal sexual intercourse is a shameful deed. It is one of the greatest of the major sins, and that it is not permissible under any circumstances. Allah has praised the successful believers in His Words:
"And those who guard their chastity (i.e., private parts, from illegal sexual acts)"

So it is an obligation upon the Muslim to guard his private parts from that which is forbidden, and it is also incumbent upon him to avert his gaze, and to stay away from the causes of shameful deeds, such as looking at disgraceful, depraved films. He must also strive to keep himself chaste by legitimate marriage, because that is better in order to avert one's glance and to preserve the private parts.

Whoever is unable to do so should fast, because it is a protection for him, as reported in the Hadith. And when he allows himself to be seduced and commits illegal sexual intercourse, he must repent and express regret. However, his prayer is not invalidated, nor are his good deeds.

And Allah is the Granter of success.

Source:
Ibn Jibreen
Fatawa Islamiyah, Vol. 6 Pages 198-199