The Sharee‘ah rule states that the conclusion of the marriage contract with a woman immediately renders her mother unlawful for her daughter’s husband forever. This is unanimously agreed-upon by the majority of scholars, but I have read in some books of Tafseer (Tafseer ibn Katheer) that there are authentic narrations from revered Muslims such as ‘Ali ibn Abi Taalib, Zayd ibn Thaabit, Ibn ‘Abbaas, ‘Abdullaah ibn Az-Zubayr, Mujaahid, and Sa‘eed ibn Jubayr stating that one can marry the mother of his wife, with whom he did not consummate his marriage.
Is it permissible for one to adopt this opinion without being sinful?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

The majority of scholars, including the Hanafi, Maaliki, Shaafi‘i and Hanbali scholars, are of the opinion that if a man marries a woman, her mother and her foster mother become unlawful for  him to marry. This also applies to the wife’s maternal and paternal grandmothers. All of those women become unlawful for this man to marry as soon as he concludes the marriage contract, as Allaah The Almighty Says (what means): {Prohibited to you [for marriage] are your mothers, your daughters, your sisters, your father's sisters, your mother's sisters, your brother's daughters, your sister's daughters, your [milk] mothers who nursed you, your sisters through nursing, your wives' mothers} [Quran 4:23]

All the honorable companions who adopted a different opinion took it back, except ‘Ali .

In his book Al-Umm, Ash-Shaafi‘i said, ‘Maalik reported that Yahya ibn Sa‘eed said, “A man asked Zayd ibn Thaabit whether it is permissible for a man, who divorced his wife before the consummation of the marriage, to marry his wife’s mother? Zayd answered, ‘No, the prohibition of marrying the mother of one’s wife is general and unconditioned, contrary to the stepdaughter.’”

Adopting the opinion that contradicts the opinion of the majority of scholars in this issue is impermissible, because the latter is unanimously agreed-upon.

In his book of Tafseer (exegesis), Imaam Al-Qurtubi said, “The majority of the righteous predecessors are of the opinion that a man’s conclusion of the marriage contract with a woman immediately renders her mother unlawful for him to marry forever. On the other hand, marrying a woman does not render her daughter unlawful for the husband to marry as long as the marriage is not consummated. This is the opinion of the senior scholars of Fatwa (religious verdict) everywhere.”

Al-Qurtubi then referred to the other opinion commenting, “This contradicts the opinion of the majority of scholars which is the adopted opinion.”

Ibn Katheer referred to the fact that Ibn ‘Abbaas and Ibn Mas‘ood withdrew their opinions, and then commented, “This is the opinion of the four Imaams and the seven Islamic jurists.” 

Allaah Knows best.