Musnad Ahmad 788:57

Muhammad ibn Ja’far narrated to us, ‘Awf and Hammad ibn Usamah narrated to us, ‘Awf narrated to me, from Ziyad ibn Mikhraq, from Abu Kinanah, from Abu Musa, who said: The Messenger of Allah (peace and blessings of Allah be upon him) stood at the door of a house in which there was a group of Quraysh. He took hold of the two doorposts and said, "Is there anyone in the house except a Qurayshi?" It was said, "O Messenger of Allah, except for so-and-so, the son of our sister." He said, "The son of a people’s sister is one of them." He then said, "This matter shall remain with the Quraysh as long as they show mercy when asked for mercy, act justly when they judge, and act equitably when they divide. Whoever among them does not do that, upon him shall be the curse of Allah, the angels, and all of mankind; neither a mandatory act nor a supererogatory act shall be accepted from him."