Praise be to Allah.
Zina is one of the worst of haraam actions and is one of the greatest of major sins. Allaah has issued a warning to the mushrikeen, those who kill unlawfully and those who commit zina of a double punishment on the Day of Resurrection and an eternity of punishment in which they will be humiliated because of the gravity of their crime and the abhorrence of their actions, as Allaah says (interpretation of the meaning):
“And those who invoke not any other ilaah (god) along with Allaah, nor kill such person as Allaah has forbidden, except for just cause, nor commit illegal sexual intercourse ___ and whoever does this shall receive the punishment.
69. The torment will be doubled to him on the Day of Resurrection, and he will abide therein in disgrace;
70. Except those who repent and believe (in Islamic Monotheism) …”
The one who has fallen into any of these sins has to repent sincerely to Allaah and follow that with sincere faith and righteous deeds. Repentance is sincere when the penitent gives up the sin, regrets what he has done in the past and resolves firmly and sincerely not to go back to it, out of fear of Allaah and veneration of Him, and in hope of His reward and for fear of His punishment. Allaah says (interpretation of the meaning):
“And verily, I am indeed forgiving to him who repents, believes (in My Oneness, and associates none in worship with Me) and does righteous good deeds, and then remains constant in doing them (till his death)”
What every Muslim man and woman must do is beware of this grave evil and the things that lead to it, and they must hasten to repent sincerely from anything of that that they have done in the past. Allaah accepts the repentance of those who repent sincerely and forgives them. End quote.