It is narrated from Sayyiduna Abu Ayyub (may Allah be pleased with him) that the Prophet (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 / 3937