One of the major reasons for confusion about the status of the Sunnah is a failure to distinguish between the word sunnah as used in its different contexts and disciplines. In particular, the usage of the jurists has led many to believe that, as some have explicitly said, "Whatever comes from the Qur'aan must be applied. If one also applies the Sunnah, that is good but is not mandatory." Some have also expressed that only the Qur'aan can establish something as obligatory and the sunnah can only establish something as recommended. It is important, therefore, to give some examples that may remove this misunderstanding.
The first example deals with Allaah's سبحانه وتعالى statement in the Qur'aan,
"O you who have believed! When you contract a debt for a fixed period, write it down." [Sooratul Baqarah, 2:282]
According to the majority of the scholars, the command here to record the transaction is one of recommendation and not obligation. Hence, the recording of such a transaction is considered, in the jargon of the jurists, a "sunnah" or non-obligatory but recommended act, even though the source for the act is found in the Qur'aan. 
Another example comes from later in the same verse:
"And take witnesses whenever you make a business dealing." [Sooratul Baqarah, 2:282]
This command from the Qur'aan is, once again, for an act that is recommended and not obligatory. Hence, even though the source for the act is a Quranic verse, that does not necessarily imply that the act is obligatory. 
On the other hand, one can note the example of the beard. There is no explicit verse in the Qur'aan referring to the beard. Yet it is covered in the sunnah or statements of the Prophet صلى الله عليه وسلم. The Prophet صلى الله عليه وسلم said, "Trim the moustache and leave the beard." 
Based on this statement, and many others of the Prophet صلى الله عليه وسلم, the majority of scholars consider the beard to be obligatory. 
In this case, therefore, one finds something only in the sunnah or statements of the Prophet صلى الله عليه وسلم but the ruling for that act is not "sunnah" in the jurists' use of the word. Instead, the ruling is that the act is obligatory or, in the terminology of the jurists, waajib. 
Another example of this nature is Zakaatul Fitr or the zakaah that is paid at the end of the month of Ramadhaan. Imaam al-Bukhaari رحمه الله and Imaam Muslim رحمه الله record from Ibn 'Umar رضي الله عنهما that the Prophet صلى الله عليه وسلم obligated the Muslims to pay the zakaatul fitr at the end of Ramadhaan. Based on this narration and others similar to it, there is a consensus that zakaatul fitr is obligatory (waajib). There is absolutely no reference to zakaatul fitr in the Qur'aan but there is still a consensus that it is obligatory. 
In essence, the source or text for an act is irrelevant with respect to the ruling of the act - whether it be obligatory or recommended ("sunnah" in the usage of the jurists). A verse in the Qur'aan may describe a specific act and that act may only be considered "sunnah". On the other hand, a statement of the Prophet صلى الله عليه وسلم, which one could call a "sunnah," could determine that an act is obligatory. The source of the common confusion on this point is that the word "sunnah" is being used with two implications or according to two different technical definitions. 
 For the ruling concerning the recording of debts and future obligations, see Kuwaiti Ministry of Religious Endowments and Religious Affairs, al-Mausoo'ah al-Fiqhiyyah (Kuwait: 1992), vol. 21, p. 123. It is true that at-Tabari رحمه الله, Ibn Hazm رحمه الله and some others interpret the command to mean one of obligation. Their conclusion does not affect the point above: the scholars understood that simply because something is found in the Qur'aan, that does not automatically make that act obligatory; it could possibly be recommended or "sunnah".
 The evidence for the non-obligatory nature of taking witnesses for business transactions is in the practice of the Prophet صلى الله عليه وسلم himself. Cf., Mustafa Salaama, At-Tasees fee Usool al-Fiqh ala Dhau al-Kitaab was-Sunnah (Cairo: Maktabah al-Haramain lil Uloom an-Naafiah, 1415 A.H.), p. 42.
 Saheeh al-Bukhaari
 For a discussion on the ruling concerning the beard, see 'Umar al-Ashqar, Thalaath Sha'aair (Kuwait: ad-Daar as-Salafiyyah, 1985), pp. 33-46. He notes (p. 45) that Ali Mahfoodh stated (and quoted his sources) that the four schools of fiqh all agree that it is forbidden to shave the beard.
 See also:
Status of the Beard: www.muftisays.com/forums/12-virtues/5070-status-of-the-be...
Once Upon a Beard: www.muftisays.com/forums/13-articles--stories--more/5566-...
 Sa'di Abu Jaib, after stating that there is a consensus on the obligation of zakaatul fitr, notes a couple of scholars who considered it to be an abrogated practice. Abu Jaib notes that their evidence is weak, to say the least. Hence, their opinions on this issue are considered anomalies. See Sa'di Abu Jaib, Mausoo'ah al-Ijmaa fee Fiqh al-Islaami (Beirut: Daar al-Arabiyyah, n.d.), vol. 1, p. 519.
 The Authority and Importance of the Sunnah