“And whosoever contradicts and opposes the Messenger, after the right path has been shown clearly to him, and follows other than the Path of the Believers; We shall keep him upon the path he has chosen, and roast him in Hell. What an evil destination!” [Sooratun-Nisaa‘ 4:115]
Most muslims regardless of their culture will tell you and believe that one of the most fundamental tenets of Islam is that we understand the religion using The Quran (The Book of Allah) and The Sunnah (The sayings, actions, approval and disapproval authentically reported from the Prophet Muhammad). What is either unknown, forgotten or neglected is that Allah has also commanded and warned us that we should also know, study and follow “The Path of the Believers.” The “believers” in this case are none other than the Sahaba (Allah be pleased with all of them), the companions of the Prophet Muhammad (Allah send the prayers and blessings of peace upon him). They were the ones who were eyewitnesses to revelation, they saw how the Prophet (sal Allahu ‘alayhi wa sallam) treated his family, his children and grandchildren, wives, relatives (both muslim and non-muslim), political leaders, elders etc. They were the ones taught, as Abdullah ibn Umar ibn al-Khattab (radhi-Allah ‘anhumma) said: “what to think about a verse (from the Quran) and what our stance should be towards it” as we have reproduced here in another blog entry. They were the ones who applied and explained the Quran after the death of the Prophet (sal Allahu ‘alayhi wa sallam) to thousands upon thousands of new muslims in dozens of lands and cultures.
So yes, may Allah be pleased with all of the companions of the Prophet Muhammad (sal Allahu ‘alayhi wa sallam) and may Allah guide us to follow His Book, the Sunnah of His Messenger, and the Understanding of these Two Sources of Islam with the understanding of the Companions of the Prophet (sal Allahu ‘alayhi wa sallam). This is Salafiyya – the methodology of understanding and applying the Book of Allah and the Sunnah with the understanding and application of the Prophet (sal Allahu ‘alayhi wa sallam) and his companions and all those who followed them exactly.
The following is the advice given by the great Muslim, a righteous predecessor without doubt, ‘Umar ibn ‘Abdul-‘Azeez, may Allah have mercy upon him, and forgive him of any mistake or sin he committed, and raise his rank in Paradise. The advice is on following the Sunnah, not innovating into it, and admonishment to follow those who preceded the muslims of their day which were the sahaba.
From Shihaab Ibn Khiraash  who said: ’Umar Ibn ’Abdul-’Azeez (d.101H) – rahimahullaah – wrote to a man,
May peace be upon you, to proceed:
So verily I advise you to fear Allaah, and to make His Command the objective, and to follow the Sunnah of His Messenger, and to leave off what people invented after him (sallallaahu ’alayhi wa sallam), from whatever is confirmed as his Sunnah, and his supply will suffice you.
Then know that there cannot ever be any innovation, except that a proof against it has already passed, and there is a warning in it. So adhere strictly to the Sunnah, for verily the Sunnah is – with the permission of Allaah – a protection for you. Verily the one who practices the Sunnah is one who indeed knows what opposes it from mistakes and error, and foolishness, and deep thorough study.
So be pleased with for yourself what the people (i.e. the Salafus-Saalih) were pleased with for themselves, for verily they stopped upon knowledge, and they sufficed with penetrating insight, and they were the strongest in studying the matters, and the virtue that was in them, in that case, they were the most adequate; since they (the Salafus-Saalih – Righteous Predecessors) have already preceded. So indeed the guidance is not what you are upon, rather they preceded you to it. Therefore you say, he innovated a newly invented matter after them, so no one invents something, except that he opposes their path, and considers himself to be better than them. Indeed whatever they spoke was sufficient, and whatever they described was satisfying. So whatever is below them is deficient, and there is no good above them. Indeed people fell short of their mark, so they became dull, and others were too ambitious, so they went into extremes, and verily they (the Salaf) were in between the two, so they were upon the straight guidance. 
From Imaam Maalik  (d.179H) – rahimahullaah – who said: ’Umar Ibn ’Abdul-’Azeez used to say,
The Messenger of Allaah (sallallaahu ’alayhi wa sallam) and the caretakers of the affairs (wulaatul-umoor) enacted Sunnahs, taking to them is affirmation (tasdeeq) of the Book of Allaah, and the completion of obedience to Allaah, and strength upon the Religion of Allaah. [And it is not for anyone to change it, nor to replace it, nor to oppose anything from it.] Whoever seeks guidance through them will be guided, and whoever seeks aid through them will be victorious, and whoever opposes them; he follows a path other than the Path of the Believers, and the close allies (wulaat) of Allaah are not with him, and his destination is Hell, and an evil end.
Maalik said, “I was amazed at ’Umar when he obligated the Fire for such a person.”
 He is Shihaab Ibn Khiraash Ibn Hawshab ash-Shaybaanee, from Koofah. He moved to Shaam, and lived in ar-Ramlah inside of Palestine, and he died there. He was sadooq (truthful), a person of the Sunnah. Refer to Tahdheebul-Kamaal (12/568-572).
 Related by Ibn Battah in al-Ibaanah (1/321-322), and by al-Laalikaa‘ee in Sharh Usoolul-I’tiqaad (no. 16)
 This is Imaam Maalik Ibn Anas, Imaam Daarul-Hijrah (the scholar of the place of migration, i.e. al-Madeenah)
 The proof for this is the statement of Allaah, “And whosoever contradicts and opposes the Messenger, after the right path has been shown clearly to him, and follows other than the Path of the Believers; We shall keep him upon the path he has chosen, and roast him in Hell. What an evil destination!” [Sooratun-Nisaa‘ 4:115]
 Related by Ibn Battah in al-Ibaanah (1/352-353)