Kaum Muslimin sepakat bahwa Sunnah Nabi Muhammad ﷺ adalah sumber kedua dari dua sumber pokok wahyu dalam Islam, setelah Al-Qur'an Al-Karim. Sunnah yang sahih terhimpun dalam khazanah literatur Hadis yang sangat luas.1

The Muslims are agreed that the Sunnah of the Prophet Muhammad (may Allah bless him and grant him peace) is the second of the two revealed fundamental sources of Islam, after the Glorious Qur'an. The authentic Sunnah is contained within the vast body of Hadith literature.1.

Hadits (jamak: ahadits) terdiri dari dua bagian: matan (teks) dan isnad (rangkaian para perawi). Sebuah teks mungkin tampak logis dan masuk akal, tetapi agar dapat diterima ia memerlukan isnad yang sahih dengan para perawi yang terpercaya. 'Abdullah bin al-Mubarak (w. 181 H), salah seorang guru terkemuka Imam al-Bukhari, berkata, "Isnad adalah bagian dari agama. Seandainya tidak ada isnad, niscaya siapa pun yang mau akan berkata apa saja yang ia kehendaki."2.

A hadith (pl. ahadith) is composed of two parts: the matn (text) and the isnad (chain of reporters). A text may seem to be logical and reasonable but it needs an authentic isnad with reliable reporters to be acceptable; 'Abdullah b. al-Mubarak (d. 181 AH), one of the illustrious teachers of Imam al-Bukhari, said, "The isnad is part of the religion: had it not been for the isnad, whoever wished to would have said whatever he liked."2.

Selama masa hidup Nabi (semoga Allah memberinya rahmat dan kesejahteraan) dan setelah wafatnya, para Sahabatnya biasa merujuk langsung kepadanya ketika mengutip sabdanya. Para Tabi'in mengikuti kebiasaan ini; sebagian dari mereka mengutip Nabi ﷺ melalui para Sahabat, sementara yang lain menghilangkan perantara di antara mereka - hadis semacam ini kemudian dikenal sebagai mursal. Ditemukan bahwa mata rantai yang hilang antara Tabi'in dan Nabi ﷺ bisa berupa satu orang, yaitu seorang Sahabat, atau dua orang, dengan orang tambahan itu adalah Tabi'in yang lebih tua yang mendengar hadis tersebut dari Sahabat. Inilah contoh bagaimana kebutuhan untuk memverifikasi setiap isnad muncul; Imam Malik (w. 179) berkata, "Orang pertama yang menggunakan isnad adalah Ibnu Syihab az-Zuhri" (w. 124).3.

During the lifetime of the Prophet (may Allah bless him and grant him peace) and after his death, his Companions (Sahabah) used to refer to him directly, when quoting his sayings. The Successors (Tabi'un) followed suit; some of them used to quote the Prophet (may Allah bless him and grant him peace) through the Companions while others would omit the intermediate authority - such a hadith was later known as mursal. It was found that the missing link between the Successor and the Prophet (may Allah bless him and grant him peace) might be one person, i.e. a Companion, or two people, the extra person being an older Successor who heard the hadith from the Companion. This is an example of how the need for the verification of each isnad arose; Imam Malik (d. 179) said, "The first one to utilise the isnad was Ibn Shihab al- Zuhri" (d. 124).3.

Alasan lain yang lebih penting adalah pemalsuan hadis yang disengaja oleh berbagai kelompok yang muncul di tengah kaum Muslimin, untuk mendukung pandangan mereka (lihat nanti, di bawah pembahasan hadis maudu'). Ibnu Sirin (w. 110 H), seorang Tabi'in, berkata, "Dahulu mereka tidak menanyakan tentang isnad. Namun ketika terjadi fitnah (kekacauan, kekisruhan, terutama perang saudara), mereka berkata: Sebutkan kepada kami nama-nama para perawimu. Maka riwayat-riwayat Ahlus Sunnah (para pengikut Sunnah) diterima, sedangkan riwayat-riwayat Ahlul Bid'ah (para pengikut bid'ah) tidak diterima."4.

The other more important reason was the deliberate fabrication of ahadith by various sects which appeared amongst the Muslims, in order to support their views (see later, under discussion of maudu' ahadith). Ibn Sirin (d. 110), a Successor, said, "They would not ask about the isnad. But when the fitnah (trouble, turmoil, esp. civil war) happened, they said: Name to us your men. So the narrations of the Ahl al-Sunnah (Adherents to the Sunnah) would be accepted, while those of the Ahl al-Bid'ah (Adherents to Innovation) would not be accepted."4.