Assalamualaikum There are many people in South Asia who claim to be Syeds. Whether this claim is true or not is a different thing, but some of them say that it is haraam for a female Syed to marry a non-Syed boy. They say that Syed girls have the status of mothers (and according to some, sisters) of non-Syeds. I believe that Islam doesn't accept caste-based discrimination, but I want proofs from the Quran and Sahih Hadith to correct them.

Alaikumassalam wa rahmatullah,

That has no basis in Islam. Syeds claim descent from the grandsons of the Prophet PBUH, and we know that the daughters of these grandsons married people unrelated to the Prophet’s family PBUH. If that was acceptable for them, it should be acceptable for all descendants of the Prophet PBUH. There is nothing in the Quran or Sunna that prevents the descendants of the Prophet PBUH from marrying non-descendants.