Mukhtasar Bukhari

Narrated by Sayyiduna Abu Shurayh (may Allah be pleased with him): The Prophet Muhammad (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, "O Messenger of Allah! Who is that person?" He (peace be upon him) replied, "The one whose neighbor is not safe from his harm."