In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

The Messenger of Allaah [peace and blessings of Allaah be upon him] said, “Indeed, the one who lives long amongst you will see a lot of differences, and beware of newly invented matters [in the religion] because it is misguidance. So whoever amongst you reaches that, then upon him to hold onto to my Sunnah and the Sunnah of the rightly guided khulafaa, and bite onto it with the molar teeth”. (1)

Imaam Ibn Ibn Rajab [may Allaah have mercy upon him] said, “In this hadeeth is [the] command that when splitting and differing occurs, [one should] adhere to the Sunnah of the Messenger [sallal-laahu-alayhi-wasallam] and the Sunnah of the khulafaa [radiyallaah-anhum] after him. The Sunnah is a path that should be adhered to and it includes that which the rightly guided khulafaa were upon in creed, actions and statements. This is the complete Sunnah”. (2)

Abdullah Ibn Mas’ood [may Allaah be pleased with him] said, “Whoever wants to adhere to a path, then let him adhere to the path of those who has passed away, for indeed the ones who are alive are not safe from trial, and they (i.e. those who have passed away) are Muhammad’s Companions. They were the best of this Ummah, the ones with the most righteous hearts, the most perfect in knowledge and the most uncomplicated. Allah selected them to accompany His Prophet [peace and blessings of Allaah be upon him] and to establish His religion. Therefore, acknowledge their status, follow their footsteps and cling as much as you can to their pattern of behaviour and attitude because they followed true guidance. (3)

Imaam Ibn Rajab [may Allaah have mercy upon him] stated: There is not to be found in the statements of those who came after the Salaf (any) truth, except that it is found in their statements with a more concise wording and a shorter expression. There is not to be found in the statements of those who came after them (any) falsehood, except that there is in their statements that which clarifies its falsity for the one who understands and contemplates [i.e. the one who understands the statements of the Salaf]. There are wonderful meanings found in their statements and precise observations, which those who came after them were neither guided to nor knew about it. The one who does not take knowledge from their statements will miss all that goodness, alongside the numerous (affairs) of falsehood he will fall into due to following those who came after them [i.e. due to abandoning the Salaf and following those who came after them]. (4)

[Ref 1: Reported by Ahmad: 4/126; Abu Daawud 4607; Tirmidhee 2676; Ibn Maajah 43]
[Ref 2: Jaami-ul Uloom Wal-Hikam: page: 249]
[Ref 3: Jaami Bayaan Al-Ilm Wa Fadlihi 2/947]
[Ref 4: Fadl Ilm As-Salaf Alaa Ilm Al-Khalaf’ page 61. slightly paraphrased]