Declaration About the Sunnah

by Imam Ash-Shaafi`ee 
Al Bayaan (The Declaration) IV
Ar-Risaalah Fee Usool al-Fiqh

Shaafi`ee said: [Al-Bayaan] includes all that the Apostle has provided in the sunna concerning which there is no [legislation in the] Book. There is in this book - concerning God's favoring mankind [with the ability] to understand the Book and Wisdom - a proof that Wisdom is the sunna of the Apostle of God.

Included in what I have stated concerning God's command to His creatures ordering obedience to the Apostle and specifiying the place it has in religion, is a proof of the precise definition of the duties stated in the Qur'aan, which consists of the following categories

The first category is what the Book has laid down with such clarity that nothing further - in addition to revelation (tanzeel) - was needed.

The second category consists in what is clearly stated in the obligation imposed [by God] ordering obedience to the Prophet. The Apostle is his turn precisely stated on the authority of God what the duties are, upon whom they are binding, and in what circumstances some of them are required or not required, and when they are binding.

The third category consists in what [God] has specified only in the sunna of His Prophet, in the absence of a textual [legislation in the] Book.

Everything [in the sunna of the Prophet] is a clear explanation for the [divine communication in the] Book of God.

So he who accepts the duties to God [laid down] in His Book should accept the sunna of the Apostle by God's command ordering His creatures to obey the Apostle and to have recourse to his decision. For he who accepts [a duty] on the authority of the Apostle accepts it from God, since God has imposed the obligation to obey [the Prophet].

The acceptance of [all the duties] laid down in both the Book of God and the sunna of the Apostle means the acceptance of each one as imposed by God, despite the differing reasons for the acceptance of what He permitted or prohibited, commanded, or punished in various ways as He pleased, glorified be His praise. For He said, "He will not be questioned about what He does, but they will be questioned." [21:23]

Source: http://www.islaam.com