Majma al-Zawaid 8987 — The caliphate is in Quraysh and people follow

Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) said: The Prophet (peace and blessings be upon him) came and stood by a house in which there were some men from Quraysh. He took hold of the two doorposts and asked: "Is there anyone in the house except Qurashis?" The people said: "No! There is also a nephew of ours (a sister's son)." The Prophet (peace and blessings be upon him) said: "The sister's son of a people is one of them." Then he said: "This matter (that is, government) will remain in Quraysh as long as, when mercy is sought from them, they show mercy; and as long as they act with justice when they judge, and act fairly when they distribute. Whoever among them does not do so, upon him will be the curse of Allah Almighty, the angels and all mankind."
Al-Tabarani recorded it in al-Mu'jam al-Saghir and al-Mu'jam al-Awsat, and its narrators are thiqat (trustworthy).