Ḥākim Nīshābūrī, one of the prominent scholars of Ahl al-Sunnah, writes about the birth of Imam Ali (peace be upon him) with the claim of tawātur (a high degree of authenticity through multiple narrations):
"The reports have reached the level of tawātur that Fāṭimah bint Asad gave birth to Amīr al-Mu’minīn Ali ibn Abī Ṭālib (may Allah honor his face) inside the Ka‘bah."
Alkarbala