Imam al-Shafiʿi and other leading scholars have adduced many proofs for this—though this is not the place to list them all. What matters is that you first seek the Quran’s commentary from the Quran itself; if you do not find it, then look to the Sunnah. The Messenger of Allah (peace and blessings be upon him) said to Muʿadh when he dispatched him to Yemen: “According to what will you judge?” Muʿadh replied, “By the Book of Allah.” He asked, “And if you do not find it?” He replied, “By the Sunnah of the Messenger of Allah.” He then asked, “And if you do not find it?” Muʿadh replied, “I will exercise my own reasoning.” The Prophet ﷺ struck him on the chest and said, “Praise be to Allah who has guided the messenger of the Messenger of Allah to what pleases the Messenger of Allah.”(1) This ḥadith is found in the Musnads and Sunan with a sound chain of transmission.

Commentary

Some scholars have spoken against this ḥadith and declared it weak, but the author holds that its chain is sound—and that appears correct—because it accords with the general principle of the Sharia: a person first rules by the Book of Allah; if he does not find a ruling there, then by the Sunnah of the Messenger of Allah ﷺ. In fact, there are matters in the Sunnah that the Quran has not spelled out and that are not apparent in the Quran, so one must refer back to the Sunnah. If a matter is found in neither of these two sources, a person then “exercises his reasoning”—meaning not that he judges by sheer opinion, but that he strives to relate the specific case or incident to the texts of the Book and the Sunnah. Thus, this ḥadith is fully in line with the general legal principles of the Sharia. Those who weakened it assumed that the phrase, “And if you do not find it, then by the Sunnah of the Messenger of Allah,” that