This, then, is taken as proof in Mālik’s school, and it is the very position expressly stated by al-Shāfiʿī. In the narration transmitted by Yūnus ibn ʿAbd al-Aʿlā he says: “When you find the early people of Medina adhering to something, harbor no doubt in your heart that it is the truth.”

The apparent doctrine of Aḥmad is the same: whatever the Rightly Guided Caliphs instituted is a binding proof that must be followed. Aḥmad declared, “Every pledge of allegiance concluded in Medina is a caliphate upon the prophetic model.” It is well known that the pledges to Abū Bakr, ʿUmar, and ʿUthmān were all given in Medina, and that the pledge to ʿAlī was likewise made there before he later left the city; thereafter no further pledge was contracted in Medina…

He goes on to say: “As for the fourth level, it is the later practice of Medina. Is this a legal proof that must be followed or not? The leading Imams agree that it is not a binding proof. This is the view of al-Shāfiʿī, Aḥmad, Abū Ḥanīfah, and others. In his book Usūl al-Fiqh and elsewhere he records that this later practice is neither consensus nor proof according to the critical scholars among Mālik’s own companions…”

I remark: The same four-tier classification is mentioned by al-Zarkashī in al-Baḥr al-Muḥīṭ (6/447); see also al-Shinqīṭī’s Mudhakkirah (p. 182).

Consensus of the Four Caliphs
Abū’l-Ḥasan al-Baʿlī says in al-Qawāʿid al-Nūrāniyyah wa’l-Fawāʾid al-Uṣūliyyah (p. 294): “The agreement of the Four Caliphs on a ruling while another mujtahid Companion disagrees with them is neither consensus nor proof according to Aḥmad and the majority of jurists. A second report from Aḥmad—may Allah have mercy on him—states that it is consensus; this was also the view of Abū Khāzim the Ḥanafī and was preferred by Ibn al-Bannāʾ among our colleagues. A third report from Aḥmad holds that it is proof, though not consensus.” End quote.

Dr. ʿAbd Allāh al-Turkī, in “The Foundations of the School of Imām Aḥmad” (p. 382), states: “The view I consider stronger is that Aḥmad—may Allah have mercy on him—did not regard their agreement as consensus, for the reports transmitted from him about choosing, when the Companions differ, the statement closest to the Book and the Sunnah are explicit and numerous. Among them is his statement in the narration of al-Marwazī: If the Companions of the Messenger of Allah ﷺ differ on a matter, it is not permissible for a man to adopt …”