(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. (JA)
Reference (JA): Sunan Abi Dawud 2885 (JA)
In-book reference (JA): Book 19, Hadith 1 (JA)
English translation (JA): Book 18, Hadith 2879 (JA)