The first generations of Muslims are collectively referred to as the "Pious Predecessors" (as-Salaf as-Saleh), and include the "Companions" (sahabah), the "Followers" (Tabi'un) and the "Followers of the Followers" (Tabi‘ al-Tabi‘in). These are revered in Sunni Islamic orthdoxy and their example used in understanding the texts and tenets of Islam by sunni theologians since the fifth Muslim generation or earlier, sometimes to differentiate the creed of the first Muslims from subsequent variations in creed and methodology (see madhab), to oppose religious innovation (bida'h) and, conversely, to defend particular views and practices.
Imaam al-Asbahanee [d.535H] - rahimahullaah - said:
“The sign of Ahlus-Sunnah is that they follow the Salaf as-Salih and abandon all that is innovated and newly introduced into the Deen.”
Imaam Muhammad Naasir-Uddin al-Albaanee [d.1420H] - rahimahullaah - said:
“However, there are some who claim knowledge who deny this ascription, claiming that it has no foundation, saying:
“It is not permissible for a Muslim to say: I am Salafee.” And it is as if he is saying: “It is not permissible for me to say: I am following the Salaf as-Salih in what they were upon in ‘aqeedah, worship and manners!” And there is no doubt that the likes of this denial - if that is what is meant- implies that he is disassociating himself from the correct Islaam that Salaf as-Salih were upon….Thus it is not permissible for a Muslim to disassociate himself from being ascribed to the Salaf as-Salih. If, however, he freed himself from any other nisbah (ascription), then none of the people of knowledge could accuse him of disbelief or sinfulness.
However, the one who refuses calling himself with this name Salafee, then it should be seen, does he attribute himself to a particular madhab - whether in matters of ‘aqeedah or fiqh? So perhaps he will call himself an Ash’aree or a Maatareedee, or he may be from Ahlul-Hadeeth, or a Hanafee, Maalikee, Shaafi’ee or Hanbalee - from those matters which enter into the term Ahlus-Sunnah wal-Jama’ah. Despite the fact that the one who ascribes himself to the Ash’aree madhab, or the four well known madhabs, then he has ascribed himself to those who are not protected from making mistakes as individuals - even though there are from them Scholars that attain what is correct.
So why! O why! do they not reject the likes of these ascription’s to individuals who are not protected from mistakes?
However, as for the one who ascribes himself to the Salaf as-Salih collectively - then he ascribes himself to that which is protected from mistakes.” [AlAsaalahMagazin(no.9/p87)]
Saalih bin ‘Abdillaah Al-‘Abood, said: “What is intended by the term ‘Salafiyyah’ is: Following the way of the Pious Predecessors (Salaf as-Saalih) of this Muslim ummah, who are in fact Ahlus-Sunnah wal-Jamaa’ah. This means uniting oneself and gathering others upon the following of the Sunnah of Allaah’s Messenger (sallAllaahu ‘alayhi wa sallam), in hidden and in open, and following the way of the first and foremost from the Muhaajireen and Ansaar, who followed them in goodness.”
The usage of the word itself can be traced as far back as to Muhammad saws, who himself has reported to have said,
”I am the best Salaf for you.”