He is not a believer whose neighbour is unsafe from his mischief

An Ansar (emigrant) came to the Holy Prophet (S) and said that he has recently purchased a house in a particular area and that his nearest person was such that he had no hope of any goodness from him and that he felt unsafe from his mischief. The Messenger of Allah (S) told ‘Ali (a.s.), Salman, Abu Zar and Miqdad to go to the Mosque and announce: “He is not a believer whose neighbour is unsafe from his mischief.” They announced it thrice and then the Messenger of Allah (S) pointed towards forty doors to his right and forty to the left indicating that forty houses in every direction constitute ones neighbourhood. One is obliged to observe their rights. ( Al – Kafi vol 2 pg 666 )  Reference : Greater Sins Volume 3