Answered by Shaykh Faraz A. Khan
Question: Did the Prophet (peace be upon him) discourage marrying relatives (ie. cousins) even though it is lawful?
Answer: Assalamu alaikum wa rahmatullah,
I pray this finds you in the best of health and states.
The short answer is that there are certain narrations that discourage marrying cousins, yet experts of hadith verification have determined them to be extremely weak or fabricated.
The Narrations in Question
– “Do not marry within the family [i.e., cousins], as that leads to children that are thin and weak.”
– “Do not marry within the family [i.e., cousins], since the child would be born thin and weak.”
– “Marry outside the family, lest the offspring be thin and weak.” [Ibn Hajar, Talkhis al-Habir]
Regarding these and similar narrations, the 7th century hadith specialist Ibn Salah said, “I found no reliable basis for them.” Many eminent hadith masters mentioned his statement and concurred, such as Ibn Hajar al-Asqalani, Ibn Mulaqqin, and others. [Ibn Hajar, Talkhis al-Habir; Ibn Mulaqqin, Khulasat al-Badr]
Taj al-Subki said regarding these narrations, “I found no chain of transmission (isnad) for them.” [Subki, Ahadith al-Ihya Alati La Asla Laha]
Hence it can be concluded that these narrations — as statements of the Prophet (peace and blessings be upon him) — are fabricated.
After mentioning Ibn Salah’s verdict, Hafiz Iraqi does state that it was rather Sayyidina Umar who made such a statement, specifically in response to a certain family/tribe whose offspring were thin and weak. He said, “You all have become thin and weak, so marry outside the family.” [Iraqi, Takhrij Ahadith al-Ihya’]
Incidentally, this advice from Sayyidina Umar corresponds with current genetic research indicating that marriage to cousins in successive generations is associated with increased likelihood of disability in offspring.
Also, the Hanbalis in particular explicitly mention that it is recommended (mustahabb) for a man to marry outside the family, as doing so normally leads to healthier and stronger offspring. [Mawsu`a Kuwaitiyya]
The Legal Ruling
As a legal ruling however, marrying one’s cousin is completely lawful in Islam, based on the Qur’an, Noble Sunna, and scholarly consensus (ijma`).
The categories of women one is forbidden to marry are clearly delineated in the Qur’an (see 4:22-24), and one’s cousin is not listed there.
Moreover, it is well-known that the Prophet (peace and blessings be upon him) married off his daughter Fatima to Sayyidina Ali, who was the Prophet’s cousin (Allah be pleased with them both).
And the Prophet himself (peace and blessings be upon him) married his first cousin, Zaynab bint Jahsh (Allah be pleased with her), as she was the daughter of the Prophet’s paternal aunt Umaymah.
Of course, the permissibility does not necessarily mean that such marriages are encouraged in the Sacred Law, especially when repeated over generations. As mentioned above, there are often health concerns if first cousin marriages continue over several generations. A physician should be consulted in particular cases.
This answer sheds more light on the issue:
And Allah knows best.
Checked & Approved by Faraz Rabbani