All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and messenger.
We have already clarified in Fataawa 31243, 33112 and 33344 that it is prohibited for a Muslim to accuse his fellow Muslim of disbelief and we highlighted its gravity there.
The sin is even greater when committed by a Muslim against his neighbor. Indeed, a neighbor has greater rights whether he is a relative or a stranger. The Quran and Sunnah recommends Muslims to be kind to neighbors. Allaah says (what means):{Worship Allaah and associate nothing with Him, and to parents do good, and to relatives, orphans, the needy, the near neighbor, the neighbor farther away,…..} [Quran 4:36]
Ibn ‘Umar related that the Prophet said: “Jibreel (Gabriel) kept recommending me to treat the neighbor with kindness until I thought that he would assign a share of inheritance to him (i.e. make the neighbor an heir of his neighbor).’” [Al-Bukhari and Muslim]
The best thing that we recommend in this case is piety and patience, [as by those things] a Muslim attains the status of doing good (Ihsaan). Allaah says (what means): {Indeed, he who fears Allaah and is patient, then indeed, Allaah does not allow to be lost the reward of those who do good.} [Quran 12: 90]
For more information on the commendable consequences of patience, please refer to Fatwa 83577.
This person who is harming you should be advised gently and in a soft manner, and it should be clarified to him that what he is doing is very serious. If there is no one to advise him, or if he is advised but he does not take heed, then the case should be referred to the authorities, with the hope that this might deter him. If this is not possible, then there is no other alternative except being patient and repelling the bad deed with a good deed. This conduct is expected to lead to good consequences; Allaah says (what means): {And not equal are the good deed and the bad. Repel [evil] by that [deed] which is better; and thereupon the one whom between you and him is enmity [will become] as though he was a devoted friend.} [Quran 41:34]
Ibn Katheer said (about the interpretation of the above verse) in his Tafseer (interpretation of the Quran): “That is to say that if you do good to someone who mistreats you, then this good that you do to him will lead him to have a good attitude towards you, love you, and be compassionate with you until he becomes like an intimate friend to you, who is sympathetic and kind to you, meaning he is compassionate with you and kind to you; and then Allaah says: {But none is granted it except those who are patient}, meaning that no one would accept this advice and acts according to it except the one who is patient with this, as this is hard on one’s soul, {and none is granted it except one having a great portion [of good].}, meaning who has a great share of happiness in this world and the Hereafter. 'Ali ibn Abu Talhah said quoting Ibn Abbaas regarding the interpretation of this verse: 'Allaah commanded the believers to be patient when angry, to restrain themselves when wronged or insulted, and to pardon when abused or mistreated. If they do so, Allaah will protect them from the devil, and their enemy will yield to them as an intimate friend…” [End of quote]
In case it is difficult to be patient, and you cannot bear the situation any more, then Allaah's earth is vast, so one can move to another place where one can be secure and safe and find good neighbors who have a good conduct and manners.
Allaah Knows best.