Marrying the Wife of the Father is Prohibited
Allah said,
وَلاَ تَنكِحُواْ مَا نَكَحَ آبَاؤُكُم مِّنَ النِّسَاء ...
And marry not women whom your fathers married,
Allah prohibits marrying the women whom the father married, in honor and respect to the fathers, not allowing their children to have sexual relations with their wives after they die.
A woman becomes ineligible for the son of her husband as soon as the marriage contract is conducted, and there is a consensus on this ruling.
Ibn Jarir recorded that Ibn Abbas said,
"During the time of Jahiliyyah, the people used to prohibit what Allah prohibits (concerning marriage), except marrying the stepmother and taking two sisters as rival wives. Allah sent down, وَلاَ تَنكِحُواْ مَا نَكَحَ آبَاؤُكُم مِّنَ النِّسَاء (And marry not women whom your fathers married), and, وَأَن تَجْمَعُواْ بَيْنَ الأُخْتَيْنِ (and two sisters in wedlock at the same time)." (4:23)
Similar was reported from Ata and Qatadah.
Therefore, the practice that the Ayah mentions is prohibited for this Ummah, being disgraced as an awful sin.
... إِلاَّ مَا قَدْ سَلَفَ ...
except what has already passed;
... إِنَّهُ كَانَ فَاحِشَةً وَمَقْتًا وَسَاء سَبِيلاً ﴿٢٢﴾
Indeed it was shameful and Maqtan, and an evil way.)
Allah said in other Ayat,
وَلاَ تَقْرَبُواْ الْفَوَحِشَ مَا ظَهَرَ مِنْهَا وَمَا بَطَنَ
Come not near to Al-Fawahish (shameful acts) whether committed openly or secretly. (6:151)
and,
وَلاَ تَقْرَبُواْ الزِّنَى إِنَّهُ كَانَ فَاحِشَةً وَسَآءَ سَبِيلاً
And come not near to unlawful sex. Verily, it is a Fahishah and an evil way. (17:32)
In this Ayah (4:22), Allah added, وَمَقْتًا (and Maqtan),
meaning, offensive.
It is a sin itself and causes the son to hate his father after he marries his wife.
It is usual that whoever marries a woman dislikes those who married her before him.
This is one reason why the Mothers of the Faithful were not allowed for anyone in marriage after the Messenger. They are indeed the Mothers of the Faithful since they married the Messenger, who is like the father to the believers. Rather, the Prophet's right is far greater than the right of a father, and his love comes before each person loving himself, may Allah's peace and blessings be on him.
Ata' bin Abi Rabah said that the Ayah, وَمَقْتًا (and Maqtan),
means, Allah will hate him,
... وَسَاء سَبِيلاً
and an evil way,
for those who take this way.
Therefore, those who commit this practice will have committed an act of reversion from the religion and deserve capital punishment and confiscation of their property, which will be given to the Muslim Treasury.
Imam Ahmad and the collectors of Sunan recorded that Al-Bara' bin Azib said that;
his uncle Abu Burdah was sent by the Messenger of Allah to a man who married his stepmother to execute him and confiscate his money.
