It is narrated from Sayyiduna Abu Ayyub (may Allah be pleased with him), the Companion of the Messenger of Allah (peace and blessings be upon him), that the Messenger of Allah (peace and blessings be upon him) said: "It is not lawful for a Muslim to cut off his brother for more than three days; they meet and this one turns away and that one turns away, and the better of the two is the one who greets first with salam."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 3940