(1) باب مَا جَاءَ فِي تَعْلِيمِ الْفَرَائِضِ
Narrated Abdullah ibn Amr ibn al-'As:
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. (FR)
Reference (FR): Sunan Abi Dawud 2885 (FR)
In-book reference (FR): Book 19, Hadith 1 (FR)
English translation (FR): Book 18, Hadith 2879 (FR)