It was narrated that 'Abdullah bin 'Amr said:
"The Messenger of Allah (ﷺ) said: 'Knowledge is based on three things, and anything beyond that is superfluous: a clear Verse, an established Sunnah, or the rulings by which the inheritance is divided fairly.'" (DE)
English reference (DE): Vol. 1, Book 1, Hadith 54 (DE)
Arabic reference (DE): Book 1, Hadith 56 (DE)