Praise be to Allaah.
If what is mentioned in the question is true, then what can we say about a mother’s husband who is so despicable, vile and contemptible, and who is lacking in religious commitment and transgresses the limits set by Allaah? To Allaah we belong and unto Him is our return; there is no power and no strength except with Allaah.
Does he not know that Allaah has forbidden a man to marry the daughter of his wife with whom he has consummated the marriage? Allaah says (interpretation of the meaning):
“Forbidden to you (for marriage) are: your mothers, your daughters, … your stepdaughters under your guardianship, born of your wives to whom you have gone in”
Let alone committing immoral actions with her. Does this man not know of the serious threat which Allaah issues and the painful torment that awaits the zaani (adulterer, one who engages in unlawful sexual relations)? 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.
The torment will be doubled to him on the Day of Resurrection, and he will abide therein in disgrace”
Does he not know that committing adultery with one's neighbour’s wife is worse than committing adultery with any other woman? It says in the hadeeth that ‘Abd-Allaah (may Allaah be pleased with him) said: “I said, ‘O Messenger of Allaah, which sin is the worst?’ He said, ‘Setting up a rival to Allaah when He has created you.’ I said, ‘Then what?’ He said, ‘Killing your child so that he will not eat with you.’ I said, ‘Then what?’ He said, ‘Committing adultery with your neighbour’s wife.’” (Narrated by al-Bukhaari, al-Hudood, 6313).
Committing adultery with one’s neighbour’s wife is regarded as a greater sin than committing adultery with any other woman, so how about committing zina with someone who is his mahram and is forbidden to him, as this evil man has done?
Ibn Abi Shaybah said: Question on committing zina with a mahram: Hafs narrated from Ash’ath from ‘Adiyy ibn Thaabit from al-Bara’ that the Prophet (peace and blessings of Allaah be upon him) sent him to a man who had married his father’s wife, and ordered him to bring him his head. Wakee’ narrated from Hasan ibn Saalih from al-Suddi from ‘Adiyy ibn Thaabit that al-Bara’ said: “I met my maternal uncle and he was carrying a banner. I said, ‘Where are you going?’ He said, ‘The Prophet (peace and blessings of Allaah be upon him) has sent me to a man who married his father’s wife, to kill him, or to strike his neck.’”
Al-Musannaaf by Ibn Abi Shaybah, part 8, p. 380. Also narrated by al-Nasaa’i, al-Nikaah, 3279; classed as saheeh by al-Albaani in Saheeh al-Nasaa’i, 3123.
So how about if he forced this girl to do that, and committed zina with her against her will?
It is very strange that it says in the question that he is very religious, even though he has audaciously transgressed the limits set by Allaah. We ask Allaah to keep us safe and sound.
One of the basic principles of Islam which no Muslim has no excuse for not knowing is that zina – with any woman at all – is haraam and is a major sin, and it is even worse if the woman with whom a person commits zina is one whom he is permanently forbidden to marry. We seek refuge with Allaah from the things that earn His wrath and painful torment.