Marry People Of Other Nations

It is recommended to marry men/women of other nations:

1- Ibn Qudamah said:
يختار الأجنبية , فإن ولدها أنجب , ولهذا يقال : اغتربوا لا تضووا يعني : انكحوا الغرائب كي لا تضعف أولادكم
“He should choose a foreign woman (not a relative); because their children will become more fertile, therefore it is narrated: اغتربوا لا تضووا “Marry a foreign woman, not a relative” so that your children do not become weak.”
[“Al-Mughni”, 7/83].

2- Imam Shafi’ii said:
ليس من قوم لا يخرجون نسائهم إلى رجال غيرهم ولا يخرجون رجالهم إلى نساء غيرهم إلا جاء أولادهم حمقى
“There is no nation that does not marry its women to men of other nations/tribes, nor its men to women of other nations/tribes, except that their children will be born retards.”
[“Aadaab al-Shaafi’ii”, 2/99].

3- Al-Ghazali said:
أن لا تكون من القرابة القريبة ، فإن ذلك يقلل الشهوة
“It should not be someone too close, because it lessens the desires.”
[“Ihya Ulum al-Din”, 2/41].

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The Qur’an says that God made us into nations and tribes, لتعارفوا , i.e. to know one another.

And health professionals have said: if generation after generation, people marry too close, there may be a slightly increased chance of genetic problem (although small).