It is narrated on the authority of Abu Hurayrah, may Allah be pleased with him, that the Prophet, peace and blessings be upon him said: "By Allah, he is not a believer! By Allah, he is not a believer! By Allah, he is not a believer.''
It was asked, "Who is that, O Messenger of Allah?''
He said, "One whose neighbor does not feel safe from his evil"
[Sahih Bikhari: Volume 8, Book 73, Good Manners and Form (Al-Adab), Number 45].