Sayyiduna Ma'qil bin Yasar (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Act upon the Qur'an; regard what it makes lawful as lawful and what it makes unlawful as unlawful; follow it, and do not disbelieve in anything of it. Whatever seems unclear to you, refer it back to Allah or to the ruler after me so that they may inform you. Believe in the Torah, the Injil (Gospel) and the Zabur (Psalms), and in what the Prophets were given from their Lord. And let the Qur'an and the clear explanation in it be your cure, for it is an intercessor whose intercession is accepted, and what it declares lawful is affirmed as true, and every verse of it has light until the Day of Resurrection. Listen! I was given Surah al-Baqarah from the Dhikr (the earlier Scriptures), I was given Ta-Ha and al-Tur from the Tablets of Musa, I was given the Opening of the Book (al-Fatihah) and the closing verses of al-Baqarah from a treasure beneath the Throne, and I was given the Mufassal surahs as an extra."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17659