Allah (SWT) says:

"Worship Allah and join none with him (in worship); and do good to parents, kinsfolk, orphans, Al-Masakeen (the poor), the neighbour who is near of kin, the neighbour who is a stranger, the companion by your side..." [Al-Quran 4:36]

Prophet Muhammed (SAW) is reported to have said:

"The best of companions with Allah is the one who is best to his companion, and the best of neighbours with Him is the one who is best to his neighbour." [Sahih al-Bukhari,Mufrad115]

"He will not enter Paradise from whose harm his neighbour is not safe." [Muslim, 64]

Note: Among the rights of one neighbour over another as affirmed by Islam are the initiation of greetings, visiting him if he is sick, offering condolences if calamity befalls him, congratulating him at times of joy, overlooking his mistakes, concealing his faults, bearing his annoyance with patience, giving him gifts, lending him money if he needs it, lowering one's gaze from looking at his womenfolk, and guiding him to that which will benefit him in his religious and worldly affairs.[Usool al-Deen al-Islami, by Shaykh Muhammad ibn Ibraaheem al-Tuwayjri ]