Abu Dawud Book 36, Hadith Number 4895.
Chapter : Not known.
Narated By ‘Aisha, Ummul Mu’minin : The Apostle of Allah (PBUH) said: It is not right for a Muslim to keep apart from another Muslim for more than three days. Then when he meets him and gives three salutations, receiving during that time no response, the other bears his sin.