Surah No. 17, Al Isra (Bani Israil), Ayat No. 36
وَلاَ تَقْفُ مَا لَيْسَ لَكَ بِهِ عِلْمٌ إِنَّ السَّمْعَ وَالْبَصَرَ وَالْفُؤَادَ كُلُّ أُولـئِكَ كَانَ
o عَنْهُ مَسْؤُولاً
And do not pursue that of which you have no strong reason to believe ; for every act of hearing, or of seeing or of feeling in the heart will be enquired (on the Day of Judgment).
Surah No. 49, Al Hujurat, Ayat No. 12
يَا أَيُّهَا الَّذِينَ آمَنُوا اجْتَنِبُوا كَثِيراً مِّنَ الظَّنِّ إِنَّ بَعْضَ الظَّنِّ إِثْمٌ وَلَا تَجَسَّسُوا وَلَا
يَغْتَب بَّعْضُكُم بَعْضًا أَيُحِبُّ أَحَدُكُمْ أَن يَأْكُلَ لَحْمَ أَخِيهِ مَيْتًا فَكَرِهْتُمُوهُ وَاتَّقُو
o اللَّهَ إِنَّ اللَّهَ تَوَّابٌ رَّحِيمٌ
O believers ! Avoid suspicion (speculation) as much as possible: suspicion (speculation) in some cases is a sin: and spy not on each other, nor backbite on one another. Would any of you like to eat the flesh of his dead brother ? No ; you would hate it (so hate backbiting), and fear Allah: In fact, Allah is the One Who forgives and accepts repentance, Most Merciful.
As far as possible we must avoid making suspicion or speculations on others matters, but if we speculate that a particular family is noble and very helpful then it is not prohibitted. Unneccessarily if we establish our views about bad habits of some persons or bad behaviour of some families then it is sin. Besides this if we start showing curiosity about the internal matters of some families and do spying for establishing our views then it is a big sin. Allah has Warned for not involving ourselves in back biting.
Said the Prophet Mohammad (saws) " If a person narrates the bad deeds of another person in his absence to others, it will be an act of backbiting. The companions of the prophet asked " If that person is possessing those bad deeds is it still a backbiting " the Prophet replied " If those bad deeds are narrated to that person and if he minds them then this is the backbiting, and if the evil deeds are not present, then these are allegations."
(Muslim, Abu Daud and Tirmizi)
The prophet said " If some one does backbiting of a living person and if that person came to know about this then go and apologise and if the backbiting is done for a dead person then make supplication (dua) for him for forgiveness of his sins ".