يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا إِن تَتَّقُوا ٱللَّهَ يَجْعَل لَّكُمْ فُرْقَانًا وَيُكَفِّرْ عَنكُمْ سَيِّـَٔاتِكُمْ وَيَغْفِرْ لَكُمْ ۗ وَٱللَّهُ ذُو ٱلْفَضْلِ ٱلْعَظِيمِ

This ability to tell right from wrong (furqan) is almost the same as inner realisation (ma‘rifah) or insight (basirah). The last mentioned creating an inner light in a man which enables him to see everything in its reality without his being deceived by its outward aspects. Whenever a man involves himself in anything to the point of always being careful about it, a particular sort of sensitivity develops in him which makes him recognise the favourable and unfavourable aspects of that matter. This applies to everyone, whether he be a religious man, a trader, a doctor or an engineer. If a man becomes totally devoted to his work, his inner realisation attains a degree when, without being entangled in this or that confusion, he straightway reaches the reality of the matter.Development of this divine insight (furqan) in a man is the greatest guarantee that he will be safe from evils; he will regularise his relations with God, and he finally will become entitled to the grace of God.

— Source: Tazkirul Quran (Maulana Wahiduddin Khan) via Quran.com (8:29)