The Companions of the Prophet (sallallaahu `alayhi wa sallam) used to take the ruling on different matters in their lives from the Qur’aan, which they use to learn from Rasoolullaah (sallallaahu `alayhi wa sallam). In many instances, the aayaat (verses) of the Qur’aan treat a subject in a general manner without a specific condition. Sometimes the aayaat will come as an absolute ruling without any precondition or limitation required by time, place, etc. As an example of what came in a general way in the Qur’aan is the Salaat. The Qur’aan does not mention how many Rak`ahs (units of prayer) we should make, or how to physically move during prayer, or the time for prayer. Similarly, the Qur’aan does not mention the minimum amount of money to have before giving Zakaat (charity) or the conditions by which to pay it. Many of our `Ibaadaat cannot be performed without stopping at the explanations related to the regulations, pillars, and conditions of nullification. It is thus a must to return to Rasoolullaah (sallallaahu `alayhi wa sallam) to know the rules in a comprehensive and clear manner. 

Many times, the Companions faced incidents in which the Qur’aan which had no ruling, and there was a need to return to the Prophet (sallallaahu `alayhi wa sallam) to know the ruling of such matters. It was the Prophet who was ordered by Allah (subhaanahu wa ta`aalaa) teach humanity, and it is the Prophet who is the most knowledgeable of mankind about that which Allah subhaanahu wa ta`aalaa expects from us. 

Allah (subhaanahu wa ta`aalaa) has told us about the duty of Rasoolullaah (sallallaahu `alayhi wa sallam) with respect to the Qur’aan, where Allah (subhaanahu wa ta`aalaa) said:

"And We have sent down unto thee (also) the Message; that thou mayest explain clearly to men what is sent for them, and that they may give thought."Qur’aan 16:44

Allah also made it clear to us that the duty of Rasoolullaah (sallallaahu `alayhi wa sallam) is to clarify the truth to people when there is a dispute:

"And We sent down the Book to thee for the express purpose, that thou shouldst make clear to them those things in which they differ, and that it should be a guide and a mercy to those who believe."Qur’aan 16:64

We are obligated to follow any ruling by Rasoolullaah (sallallaahu `alayhi wa sallam) in any dispute:

"But no, by the Lord, they can have no (real) Faith, until they make thee judge in all disputes between them, and find in their souls no resistance against Thy decisions, but accept them with the fullest conviction."Qur’aan 4:65

Allah also mentioned that Rasoolullaah (sallallaahu `alayhi wa sallam) was given the Qur’aan and Wisdom to teach people the regulations of their religion:

"Allah did confer a great favour on the believers when He sent among them an apostle from among themselves, rehearsing unto them the Signs of Allah, sanctifying them, and instructing them in Scripture and Wisdom, while, before that, they had been in manifest error."Qur’aan 3:164

Regarding the last aayah, most scholars and those of great knowledge said that the wisdom mentioned in the aayah means another thing besides the Qur’aan. It is what Allah subhaanahu wa ta`aalaa has given Rasoolullaah (sallallaahu `alayhi wa sallam) from the knowledge of matters and regulations that the rest of humanity can not attain. Imaam Ash-Shaafi`ee rahimahullaahhas said that, "Allah subhaanahu wa ta`aalaa has mentioned the scripture which is the Qur’aan, and he mentioned wisdom and I have learned from the people of knowledge that the wisdom here is the Sunnah of Rasoolullaah (sallallaahu `alayhi wa sallam). It is from the mercy of Allah (subhaanahu wa ta`aalaa) that He has sent to us a way to practice what is in the Qur’aan." 

Allah (subhaanahu wa ta`aalaa) did not stop by saying scripture only, but the inclusion of the Sunnah with the Qur’aan is an indication of its important and the obligation on us to follow it as we have to follow the Qur’aan. Imaam Ash-Shaafi`ee goes on saying that the letter 'wa' ('and' between Scripture and Wisdom in the aayah) is a letter of conjunctions in Arabic which requires that the two parts it joins must be different otherwise the sentence will be redundant, and Allah (subhaanahu wa ta`aalaa) is far away from that; na`oodhu billaah. And so when Allah (subhaanahu wa ta`aalaa) said that he has conferred a great favor on the believers, He does not confer anything that is not correct and truthful. Therefore, this wisdom must be followed as the Qur’aan, and Allah (subhaanahu wa ta`aalaa) has never ordered us to follow anything but Him and His messenger (sallallaahu `alayhi wa sallam). Which must mean that this wisdom is what came from Rasoolullaah (sallallaahu `alayhi wa sallam) in the form of rules and sayings regarding legislation. 

To clarify the concept of Sunnah and our obligation to follow it, Allah (subhaanahu wa ta`aalaa) said:

"Those who follow the apostle, the unlettered Prophet, whom they find mentioned in their own (scriptures),- in the law and the Gospel;- for he commands them what is just and forbids them what is evil; he allows them as lawful what is good (and pure) and prohibits them from what is bad (and impure); He releases them from their heavy burdens and from the yokes that are upon them. So it is those who believe in him, honour him, help him, and follow the light which is sent down with him,- it is they who will prosper."Qur’aan 7:157

Because this teaching is mentioned in general in this aayah, then it must include the rules in the Qur’aan and Sunnah. 

A very strong indicator of the obligation upon us to follow the Sunnah can be found in this aayah:

"...And whatsoever the Messenger (Muhammad (sallallaahu `alayhi wa sallam)) gives you, take it, and whatsoever he forbids you, abstain (from it) , and fear Allah. Verily, Allah is severe in punishment."Qur’aan 59:7

Allah has also made the obedience of Rasoolullaah (sallallaahu `alayhi wa sallam) in conjunction with the obedience to Him:

"And obey Allah and the Messenger, that ye may obtain mercy."Qur’aan 3:132

We are asked by Allah (subhaanahu wa ta`aalaa) to answer any order by Rasoolullaah (sallallaahu `alayhi wa sallam):

"O ye who believe! give your response to Allah and His Messenger, when He calleth you to that which will give you life."Qur’aan 8:24

Allah made the obedience of Rasoolullaah (sallallaahu `alayhi wa sallam) an obedience to Him, and following Rasoolullaah (sallallaahu `alayhi wa sallam) an indication of the love of Allah subhaanahu wa ta`aalaa:

"He who obeys the Messenger, obeys Allah."Qur’aan 4:80

"Say: If ye do love Allah, Follow me: Allah will love you and forgive you sins."Qur’aan 3:31

And Allah subhaanahu wa ta`aalaa warrned us from not following the instructions of Rasoolullaah (sallallaahu `alayhi wa sallam):

"Then let those beware who withstand the Messenger’s order, lest some trial befall them, or a grievous penalty be inflicted on them."Qur’aan 24:63

Not only that, but Allah (subhaanahu wa ta`aalaa) told us that disobeying Rasoolullaah (sallallaahu `alayhi wa sallam) is Kufr (disbelief):

"Say: Obey Allah and His Messenger.: But if they turn back, Allah loveth not those who reject Faith."Qur’aan 3:32

It was never allowed by Allah (subhaanahu wa ta`aalaa) that a believer disobey Rasoolullaah (sallallaahu `alayhi wa sallam) order:

"It is not fitting for a Believer, man or woman, when a matter has been decided by Allah and His Messenger to have any option about their decision: if any one disobeys Allah and His Messenger, he is indeed on a clearly wrong Path."Qur’aan 33:36

To show that not following the ruling of Rasoolullaah (sallallaahu `alayhi wa sallam) when a dispute occurs is a sign of hypocrisy, Allah (subhaanahu wa ta`aalaa) says:

"They say, We believe in Allah and in the apostle, and we obey; but even after that, some of them turn away; they are not (really) Believers. When they are summoned to Allah and His apostle, in order that He may judge between them, behold some of them decline (to come)....The answer of the Believers, when summoned to Allah and His Messenger, in order that He may judge between them, is no other than this: they say, "We hear and we obey"; it is such as these that will attain felicity."Qur’aan 24:47-51

__________________________________________________________________________________