THE MUSLIM AND HIS NEIGHBORS
Having a bad neighbor is something which is so appalling that the sensitive Muslim cannot think of it without shuddering and being filled with a sense of fear, loathing and hatred.
The bad neighbor is a person who is deprived of the blessing of faith, which is the greatest blessing that the Creator has bestowed upon His creation. The Prophet (s.a.w.s.) confirmed the bad neighbor’s loss of this great blessing in no uncertain terms when he said: “He is not a believer. He is not a believer. He is not a believer.” The people asked, “Who, O Messenger of Allah?” He said, “The one from whose evil (or troubles) his neighbor does not feel safe.” (Bukhari and Muslim)
In a report given by Muslim he (s.a.w.s.) said:
“The one from whose evil his neighbor does not feel safe will not enter Paradise.”
How great must be the crime of the bad neighbor, if his mistreatment of his neighbor is depriving him of the blessings of faith and denying him entrance to Paradise!
The true Muslim listens to these teachings with an open mind and accepts them. It never occurs to him that one day he may find himself in an argument or conflict with one of his neighbors, because that will destroy his faith and all hope of success in the Hereafter. This would be the greatest loss, and the mere thought of it makes the true Muslim tremble..
The bad neighbor is a person whose good deeds are not accepted
Not surprisingly, several hadith state that the bad neighbor is one whose good deeds are not accepted, and will be of no avail so long as he is mistreating his neighbor, because in Islam, good deeds are always centered on a foundation of faith, and as we have seen in the hadith quoted above, the bad neighbor has no faith. So obviously his good deeds are not accepted: Allah (S.W.T.) rejects them outright, no matter how many good deeds he does, even if he spends all day and all night doing them.
The Prophet (s.a.w.s.) was asked: “O Messenger of Allah, such-and-such a woman spends her nights in prayer, fasts during the day, and so on, and she gives charity, but she offends her neighbors with her sharp tongue.” The Prophet (s.a.w.s.) said:
“Her good deeds will be of no avail: she is among the people of Hell.” They said, “And so-and-so prays only the obligatory prayers, gives charity in the form of left-over curds, but does not offend anyone.” The Prophet (s.a.w.s.) said: “She is among the people of Paradise.”
The bad neighbor is one of the three worst types of people defined by the Prophet (s.a.w.s.):
“There are three worst types of people: a ruler who, if you do well, does not appreciate it and if you do wrong, he does not forgive you for it; a bad neighbor who, if he sees something good, he conceals it, and if he sees something bad he broadcasts it; and a wife who, when you are present, she annoys you and if you go away, she betrays you.” 
Hence the smart Muslim will have a very clear picture of the bad neighbor, as described by the Prophet (s.a.w.s.), and will keep a great distance from such a person.
 Reported by Bukhari in al-Adab al-Mufrad
 Reported by al-Tabarani; the men of its isnad are thiqat.