There is a woman dancing in niqab, and also a man in niqab playing an electric guitar! I was shocked. I told my son that these are both haram, but my son insisted there was nothing in the Quran about it. What should I tell him?
You son is wrong. Almighty Allah says in the holy Quran:
وَلاَ تَقْرَبُواْ الْفَوَاحِشَ مَا ظَهَرَ مِنْهَا وَمَا بَطَنَ [الأنعام : 151]
And do not go near shameful acts, whether they are open or secret.
In another verse Almighty Allah says:
وَمِنَ النَّاسِ مَن يَشْتَرِي لَهْوَ الْحَدِيثِ لِيُضِلَّ عَن سَبِيلِ اللَّهِ بِغَيْرِ عِلْمٍ الخ [لقمان : 6]
There is a man among the people who buys discourses of distracting amusements, so that he may mislead (people) from the Way of Allah, and make a mockery of it. For such people there is a disgraceful punishment.
In this verse لهوالحديث means singing a song, instruments of amusements and musical instruments and anything which diverts a man from good acts. Also hadith speaks severely against dance, and song etc. Make your son understand this and remove instruments of amusement like TV or video etc from your home.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband