Umm al-Mu'mineen Aisha (may Allah be pleased with her) narrates that the Prophet Muhammad (peace and blessings be upon him) said: "Gabriel (peace be upon him) emphasized to me so much about doing good to the neighbor that I thought he would make the neighbor an heir."
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."