The Sermon on the Mount was indeed the greatest discourse ever given on earth. It is remarkable for its spiritual content and clarity.
إِنَّ ٱلْمَوْعِظَةَ عَلَى ٱلْجَبَلِ لَأَعْظْمُ خُطْبَةٍ أُلْقِيَتْ عَلَى ٱلْأَرْضِ .‏