وَقَالَ الَّذِينَ كَفَرُواْ لَوْلاَ نُزِّلَ عَلَيْهِ الْقُرْءَانُ جُمْلَةً وَحِدَةً كَذَلِكَ لِنُثَبِّتَ بِهِ فُؤَادَكَ وَرَتَّلْنَاهُ تَرْتِيلاً - وَلاَ يَأْتُونَكَ بِمَثَلٍ إِلاَّ جِئْنَـكَ بِالْحَقِّ وَأَحْسَنَ تَفْسِيراً
(And those who disbelieve say: â€Why is not the Qur'an revealed to him all at once'' Thus, that We may strengthen your heart thereby. And We have revealed it to you gradually, in stages. And no example or similitude do they bring, but We reveal to you the truth, and the better explanation thereof.) (25:32-33) This Surah was named Al-Furqan, because it is the criterion that decides between truth and falsehood, guidance and misguidance, right and wrong, lawful and unlawful.