The Sunnah as evidence

السنة

The Sunnah is the Prophet’s ﷺ sayings, deeds, and approvals. Mutawatir Sunnah is qati in transmission — the five prayers, the amounts of zakat as a practice of the ummah. Ahad Sunnah is zanni in transmission: one or a few reliable roads. The four take ahad when the chain is sound. They differ on what it can do to the Quran, and on extra tests.

قول وفعل وتقرير
Word, deed, approval
A command in speech is the strongest. A deed may be unique to him ﷺ. A silent approval of what he saw is a dalil that the act is not haram.
المتواتر والآحاد
Mutawatir and ahad
Mutawatir: so many roads that collusion is unthinkable. Ahad: everything else, including famous (mashhur) reports Hanafis put in a middle rank.
خبر الواحد
Khabar al-wahid
Malik may set it aside if it clashes with the practice of Madinah. Hanafis may set it aside if it clashes with a general Quranic text or with the narrator’s own fatwa. Shafii and Ahmad take it when the isnad is sound.
البيان
Bayan
The Sunnah explains the Quran: how many rakahs, what to recite, when to bow. That is not extra religion. That is the Prophet ﷺ teaching the Book.

Worked example

Two rakahs before Fajr

The Quran did not number them. The Sunnah did. Nobody among the four says the Sunnah is a rival Book. They argue only when a lone report seems to add a hukm the Quran left general — and even then, Ahmad and al-Shafii usually let the report speak.

Mustalah tells you if the report is sahih. Usul tells you what a sahih report does. Open both. Nur’s Methods tab is mustalah. This book is usul.