Al-Ma'idah' - 5:101

يَا أَيُّهَا الَّذِينَ آمَنُواْ لاَ تَسْأَلُواْ عَنْ أَشْيَاء إِن تُبْدَ لَكُمْ تَسُؤْكُمْ وَإِن تَسْأَلُواْ عَنْهَا حِينَ يُنَزَّلُ الْقُرْآنُ تُبْدَ لَكُمْ عَفَا اللّهُ عَنْهَا وَاللّهُ غَفُورٌ حَلِيمٌ
[5:101]
O you who believe! do not put questions about things which if declared to you may trouble you, and if you question about them when the Quran is being revealed, they shall be declared to you; Allah pardons this, and Allah is Forgiving, Forbearing.
O ye who believe! Ask not questions about things which, if made plain to you, may cause you trouble. But if ye ask about things when the Qur'an is being revealed, they will be made plain to you, Allah will forgive those: for Allah is Oft-forgiving, Most Forbearing.
O ye who believe! Ask not of things which, if they were made unto you, would trouble you; but if ye ask of them when the Qur'an is being revealed, they will be made known unto you. Allah pardoneth this, for Allah is Forgiving, Clement.