Hadith of the thaqalayn

There exist several versions of this hadith in Sunni sources.[1] The version that appears in Musnad Ahmad, a canonical Sunni hadith collection, reads,

I [Muhammad] left among you two treasures which, if you cling to them, you shall not be led into error after me. One of them is greater than the other: The book of God (Quran), which is a rope stretched from Heaven to Earth, and [the second one is] my progeny, my Ahl al-Bayt. These two shall not be parted until they return to the pool [of abundance in paradise, kawthar].[1]

Muhammad might have repeated this statement on multiple occasions,[1][2][3] including his Farewell Pilgrimage and later at the Ghadir Khumm, shortly before his death in 632 CE.[2][4] The version of this hadith in al-Sunan al-kubra, another Sunni hadith collection, adds the warning, "Be careful how you treat the two [treasures] after me."[5] Similar versions of the hadith can be found in other major Sunni sources, including Sahih Muslim, Sahih al-Tirmidhi, and Sunan al-Darimi.[6] According to the Shia theologian Muhammad H. Tabatabai (d. 1981), the hadith of the thaqalayn has been transmitted through more than a hundred channels by over thirty-five companions of Muhammad.[7]

Shia Islam limits the Ahl al-Bayt to the Ahl al-Kisa, namely, Muhammad, his daughter Fatima, her husband Ali, and their two sons, Hasan and Husayn.[8][9] In Shia theology works, the Ahl al-Bayt often also includes the remaining Shia imams.[10] There are various interpretations in Sunni Islam, though a typical compromise is to include Muhammad's wives in the Ahl al-Bayt, in addition to the Ahl al-Kisa.[11] In some Sunni versions of the hadith, however, ahl al-bayt has been replaced with sunna, that is, practices of Muhammad.[11][12]

Some Sunni versions of the hadith of the thaqalayn replace ahl al-bayt with sunna, that is, practices of Muhammad.[11][12][13] This change is either intended to challenge the Shia implications of the hadith,[13] or, if authentic, may imply that the ahl al-bayt of Muhammad are a source of his sunna.[14] Muhammad is indeed viewed as the 'living Quran', the embodiment of God's will in his behavior and words.[15] Both Sunni and Shia Muslims uphold the Quran and the sunna of Muhammad, though Shia extends the sunna to also include the traditions and practices of their imams.[16]

Names of Muhammad, his daughter Fatima, and the Twelve Imams, inscribed on the tilework of the shrine of Ali al-Rida, the eighth of the Twelve Imams, Mashhad, Iran

In Twelver Shia, the hadith of the thaqalayn establishes a parallel between the Quran and the family of Muhammad,[13] implying that the two serve as the only sources of divine guidance after Muhammad.[17] The hadith also implicitly describes (some) descendants of Muhammad as the true interpreters of the Quran,[18] and those descendants are viewed as the living embodiments of the Quran in Twelver Shia.[13] As divine guides, those descendants must also be infallible lest they lead their followers astray.[17] The hadith also implies that Earth is never void of a descendant of Muhammad, an infallible imam, who serves as the divine guide of humankind in his time. These are the Twelve Imams in Twelver Shia.[17] The last of these imams, Muhammad al-Mahdi, is believed to remain miraculously in occultation since 874 and is expected to return in the end of times to eradicate injustice and evil.[19] Beyond the Twelvers, the belief in the eschatological Mahdi remains popular among all Muslims, possibly owing to numerous traditions to this effect in canonical Sunni and Shia sources.[19]