It is narrated from Sayyiduna Jubair bin Mut'im (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: A Quraishi has strength equal to two men compared to a non-Quraishi.
Hadith Referenceمسند احمد / مسند المدنيين رضي الله عنهم اجمعين / 16766