All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu 'alyhi wa sallam, is His slave and Messenger.
Firstly, we should explain the meaning of Salafiyyah, linguistically and culturally.
In Arabic, Salafiyyah stands for predecessors – the forbearers. However, in Islamic culture it means the Companions, Taabi‘oon (followers), and those who followed them, including the Imaams worthy of following, such as the four Imaams [Abu Haneefah, Maalik, Ash-Shaafi'i and Ahmad], Sufyaan Ath-Thawri, Al-Bukhari, Sufyaan ibn ‘Uyaynah as well as the other prominent scholars whose leadership in religion and piety are attested.
Salafiyyah is the school which derived its ‘Aqeedah (creed) and the Islamic method from the Quran and the Sunnah, according to the understanding of the righteous predecessors from among the Companions, Taabi‘oon and those who followed them in righteousness. The most distinctive characteristic of the followers of this school is their adherence to the methodology of transmission. Therefore, its followers are known as the People of Hadeeth or People of Athar, to be distinguished from those who opposed this method.
There is no doubt that the Salafi method is the one that must be followed by every Muslim. Shaykh Al-Islam Ibn Taymiyyah said that a person will not be disgraced for practicing the Salafi method and associating himself with it. Rather, he will be accepted by consensus, for the methodology of the righteous predecessors is inevitably right.
There is abundant evidence for the authenticity of this method. One of them is the verse that says (what means): {So if they believe in the same as you believe in, then they have been [rightly] guided; but if they turn away, they are only in dissension, and Allaah will be sufficient for you against them. And He is the Hearing, the Knowing.} [Quran 2:137]
According to this verse, Allaah The Almighty made belief in the same methodology as the Companions a sign of guidance, and non-commitment to it an indication of deviation.
Further evidence is the verse that says (what means): {And whoever opposes the Messenger after guidance has become clear to him and follows other than the way of the believers - We will give him what he has taken and drive him into Hell, and evil it is as a destination.} [Quran 4:115]
The "way of the believer" is the way of the Prophet, sallallaahu ‘alayhi wa sallam, and the noble Companions in terms of words, practice and belief. Allaah The Almighty prohibited opposition to it and following other practices, and threatened those who did so with Hell and an evil destination in the Hereafter.
Another evidence is the verse that says (what means): {And the first forerunners [in the faith] among the Muhajireen and the Ansar and those who followed them with good conduct - Allaah is pleased with them and they are pleased with Him, and He has prepared for them gardens beneath which rivers flow, wherein they will abide forever. That is the great attainment.} [Quran 9:100]
Allaah The Almighty praised the followers of the Companions, Saying (what means): {and those who followed them with good conduct} [9:100], for the Companions received the religion directly from the Prophet, sallallaahu ‘alayhi wa sallam, and consequently understood his goals, and they experienced with him the interaction that was unavailable to succeeding generations.
Caliph ‘Umar ibn Abd Al-‘Azeez said that we must do exactly what the Companions and the Taabi‘oon did, without deletion or addition, for they were distinguished by knowledge and insight. He added that an innovator in religion is one who opposes and neglects their path. The Companions, in his view, did all the possible good deeds, and explained and warned against all evil ones, emulating the Prophet, sallallaahu ‘alayhi wa sallam. Therefore, anyone who ignores their good deeds, claiming to be more knowledgeable than them, is a religious innovator. Anyone who is remiss in following their guidance has hardness and illness in his heart. [Abu Nu‘aym, Ibn Battah, Ibn Al-Qayyim]
Shaykh Al-Islam Ibn Taymiyyah quoted words similar to these on the authority of ‘Abd Al-‘Azeez ibn ‘Abd Allaah ibn Abi Salamah.
The Taabi‘oon and their followers adopted the methodology of the Companions. Therefore, it was reported that the Prophet, sallallaahu ‘alayhi wa sallam, said that the best of people are the Companions, then the Taabi‘oon, and then those who follow them with good conduct. [Al-Bukhari]
Ibraheem An-Nakha‘i was a Taabi‘i who said that if it came to his knowledge that the Companions refrained from doing something, even if it was little, he would abstain from it, because it is a sin to do things contrary to the actions of the Companions.
There are numerous citations narrated on the authority of the Taabi‘oon in this respect. Those who are destined to be prosperous are those who stringently follow the way of the Companions and their two successive generations.
Allaah Knows best.