The Prophet ﷺ said: Knowledge has three categories; anything else is extra; a precise verse, or an established sunnah (practice), or a firm obligatory duty.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ الْعِلْمُ ثَلاَثَةٌ وَمَا سِوَى ذَلِكَ فَهُوَ فَضْلٌ آيَةٌ مُحْكَمَةٌ أَوْ سُنَّةٌ قَائِمَةٌ أَوْ فَرِيضَةٌ عَادِلَةٌ