﴿ ٱللَّهُ نَزَّلَ أَحْسَنَ ٱلْحَدِيثِ كِتَٰبًۭا مُّتَشَٰبِهًۭا مَّثَانِىَ تَقْشَعِرُّ مِنْهُ جُلُودُ ٱلَّذِينَ يَخْشَوْنَ رَبَّهُمْ ثُمَّ تَلِينُ جُلُودُهُمْ وَقُلُوبُهُمْ إِلَىٰ ذِكْرِ ٱللَّهِ ۚ ذَٰلِكَ هُدَى ٱللَّهِ يَهْدِى بِهِۦ مَن يَشَآءُ ۚ وَمَن يُضْلِلِ ٱللَّهُ فَمَا لَهُۥ مِنْ هَادٍ ﴾

“God bestows from on high the best of all teachings in the shape of a divine writ fully consistent within itself, repeating each statement [of the truth] in manifold forms [a divine writ] whereat shiver the skins of all who of their Sustainer stand in awe: [but] in the end their skins and their hearts do soften at the remembrance of [the grace of] God. Such is God’s guidance: He guides therewith him that wills [to be guided] whereas he whom God lets go astray can never find any guide”

God has revealed the best of discourses a Book kitāban substitutes for ahsana ‘the best’ namely a Qur’ān consimilar in other words some of its parts are similar to others in terms of their arrangement and otherwise in coupled phrases — a Book in which the Promise of reward is coupled with the Threat of punishment together with other such couplings — whereat quiver at the mention of whose Threat shiver the skins of those who fear their Lord; then their skins and their hearts soften to they are reassured by the remembrance of God that is at the mention of His Promise. That Book is God’s guidance by which He guides whomever He will of His servants; and whomever God leads astray for him there is no guide.