It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "Do not cut off relations with one another, do not turn your backs on one another, do not hate one another, and be, O servants of Allah, brothers; and it is not lawful for a Muslim to forsake his brother for more than three days."
Thus Abdullah bin Budayl bin Warqa' (may Allah have mercy on him) narrated it from Imam al-Zuhri (may Allah have mercy on him), from Ubaydullah (may Allah have mercy on him), from Sayyiduna Ibn Abbas (may Allah be pleased with them both).
Whereas the other companions of Imam al-Zuhri (may Allah have mercy on him) narrated it from al-Zuhri (may Allah have mercy on him), from Ata bin Yazid (may Allah have mercy on him), from Sayyiduna Abu Ayyub (may Allah be pleased with him); and also from al-Zuhri (may Allah have mercy on him), from Sayyiduna Anas bin Malik (may Allah be pleased with him). So if Abdullah bin Budayl (may Allah have mercy on him) preserved it correctly, then this hadith is gharib (strange), and it is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) only through this route.
Hadith Referenceالمعجم الأوسط / باب الألف / 3030
Hadith Takhrij«أخرجه الحاكم فى «المستدرك» برقم: 7384، والطبراني فى «الصغير» برقم: 280، والطبراني فى «الأوسط» برقم: 8930»