Hadith 5669
Sayyiduna Abu Ayyub Ansari (may Allah be pleased with him) narrates this statement of the Noble Prophet (peace and blessings of Allah be upon him): "It is not permissible for any Muslim to remain estranged from his brother for more than three days. When the two meet, this one turns his face away and that one turns his face away. The better of the two is the one who initiates the greeting of peace (salam)."