The people of pre-Islamic times used to eat some things and leave others alone, considering them unclean. Then Allah sent His Prophet ﷺ and sent down His Book, marking some things lawful and others unlawful; so what He made lawful is lawful, what he made unlawful is unlawful, and what he said nothing about is allowable. And he recited: "Say: I find not in the message received by me by inspiration any (meat) forbidden to be eaten by one who wishes to eat it...." up to the end of the verse.  

كَانَ أَهْلُ الْجَاهِلِيَّةِ يَأْكُلُونَ أَشْيَاءَ وَيَتْرُكُونَ أَشْيَاءَ تَقَذُّرًا فَبَعَثَ اللَّهُ تَعَالَى نَبِيَّهُ وَأَنْزَلَ كِتَابَهُ وَأَحَلَّ حَلاَلَهُ وَحَرَّمَ حَرَامَهُ فَمَا أَحَلَّ فَهُوَ حَلاَلٌ وَمَا حَرَّمَ فَهُوَ حَرَامٌ وَمَا سَكَتَ عَنْهُ فَهُوَ عَفْوٌ وَتَلاَ { قُلْ لاَ أَجِدُ فِيمَا أُوحِيَ إِلَىَّ مُحَرَّمًا } إِلَى آخِرِ الآيَةِ