Answer
(Fatwa: 723/507/L=1431)
In Islam no caste has any superiority on the other one at all, one who is more pious he is more beloved near Almighty Allah.
إِنَّ أَكْرَمَكُمْ عِندَ اللَّهِ أَتْقَاكُمْ الآية [الحجرات : 13]
If somebody’s deeds threw him behind then his lineage cannot bring him forth. However, in the chapter of marriage Islam has considered equality because the customs and traditions of each caste differ from others. In marrying in ones own caste there is more chance of strong relationship between spouses. In contrary to it, in marrying in other caste there is fear of spoiling of the relationship which is against the aims and objectives of marriage. That is why Ulema have briefed that if a girl marries in such a family which is of low status than her caste according to the custom then the guardians of the girl have the right to revoke the nikah before delivery. And according to another saying the nikah does not take place. Yes, if the guardians of the girl marry her in other caste happily then nikah is valid and effective. Hence having the belief that marriage in other caste is totally unlawful and innovation is not true.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband