فَـَٔامِنُوا۟ بِٱللَّهِ وَرَسُولِهِۦ وَٱلنُّورِ ٱلَّذِىٓ أَنزَلْنَا ۚ وَٱللَّهُ بِمَا تَعْمَلُونَ خَبِيرٌ Qur’an At-Taghabun (64:8)Faaminoo biAllahi warasoolihi waalnnoori allathee anzalna waAllahu bima taAAmaloona khabeerun
i.e., the Quran.
"The Light which We have sent down": i.e., the light of Revelation, the fight of conscience, the light of reason, and every kind of true light by which we may know Allah and His Will. If we play false with any such lights, it is fully known to Allah.