Sahih al-Bukhari Book 78, Hadith 47
The Prophet (ﷺ) said, "By Allah, he does not believe! By Allah, he does not believe! By Allah, he does
not believe!" It was said, "Who is that, O Allah's Messenger (ﷺ)?" He said, "That person whose neighbor
does not feel safe from his evil."
Allah' Apostle said, Gabriel kept on recommending me about treating the neighbors in a kind and polite manner, so much so that I thought that he would order (me) to make them (my) heirs."
The Prophet (ﷺ) used to say, "O Muslim ladies! A neighbouress should not look down upon the present of her neighbouress even it were the hooves of a sheep."