Ilm al-Hadith — The Sciences of Hadith: How the Prophet's Legacy Was Preserved and Authenticated

The Classification of Hadith by Authenticity

Sahih (sound): All narrators in the chain are trustworthy (thiqa) with precise memory (dabt); the chain is unbroken; the hadith contradicts neither a stronger hadith nor reason. The six Kutub al-Sitta (the six major collections of Sunni hadith — Bukhari, Muslim, Tirmidhi, Abu Dawud, Nasa’i, Ibn Majah) are the benchmark collections.

Hasan (good): The same as sahih except one or more narrators has slightly weaker memory. Actionable in law.

Da’if (weak): A narrator has significant memory deficiencies, or there is a break in the chain, or the content contradicts established hadith. Not acted upon in binding legal rulings, though sometimes cited for virtuous practices (fada’il al-a’mal) by some scholars.

Mawdu’ (fabricated): The text or chain contains proven fabrication. Forbidden to transmit without noting the fabrication.

The Six Major Collections (Kutub al-Sitta)

1. Sahih al-Bukhari (d. 870 CE): ~7,275 unique hadith; the most authoritative collection in Sunni tradition
2. Sahih Muslim (d. 875 CE): ~7,500 unique hadith; strong focus on legal hadith
3. Sunan Abi Dawud (d. 889 CE): ~5,274 hadith; focused on legal rulings
4. Jami’ al-Tirmidhi (d. 892 CE): ~3,956 hadith; notable for narrator evaluation
5. Sunan al-Nasa’i (d. 915 CE): ~5,758 hadith; very strict chain standards
6. Sunan Ibn Majah (d. 887 CE): ~4,341 hadith; valuable for legal discussions

The Ismaili/Shia Hadith Tradition

Shia and Ismaili traditions also have their own hadith collections, transmitted through the Ahl al-Bayt chains rather than primarily through the Companions. The al-Kafi of al-Kulayni (Twelver), and Ismaili collections transmitted through the da’i tradition, apply similar but distinct chain standards and authentication criteria.

See also: Quran Sciences, Ilm Al Rijal, Nasikh Mansukh, Tafsir Overview, Hadith Types, Sahaba