The Hadith al-Thaqalayn () refers to a hadith () attributed to the Islamic prophet Muhammad that introduces the Quran and his progeny as the only sources of divine guidance after his death. Widely reported by both Shia and Sunni authorities, the Hadith al-Thaqalayn is of particular significance for the Twelver Shia, where their Twelve Imams are viewed as the spiritual and political successors of Muhammad. Hadith al-Thaqalayn There are also several slightly different versions of this hadith in Sunni sources. The version that appears in the canonical Sunni collection Musnad Ahmad is as follows: Muhammad might have repeated this statement on multiple occasions, including the Farewell Pilgrimage shortly before his death. The version of this hadith in the Sunni collection as-Sunan al-kubra also includes the warning, "Be careful how you treat the two [treasures] after me." According to the Shia Tabatabai (), the Hadith al-Thaqalayn has been transmitted through more than a hundred channels by over thirty-five of Muhammad's companions. In some Sunni versions of the hadith, the word appears instead of . Ahl al-Bayt Muslims disagree as to who belong to the Ahl al-Bayt (), a term which also appears in verse 33:33 of the Quran, known as the Verse of Purification. 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. There are various views in Sunni Islam, though a typical compromise is to include also Muhammad's wives in the Ahl al-Bayt. In Shia theology works, the Ahl al-Bayt often also includes the remaining Shia Imams. The term is sometimes loosely applied in Shia writings to all descendants of Ali and Fatima. Inclusion of the Ahl al-Kisa The majority of the traditions quoted by al-Tabari () in his exegesis identify the Ahl al-Bayt in the Verse of Purification with the Ahl al-Kisa, namely, Muhammad, Ali, Fatima, Hasan, and Husayn. These traditions are also cited by some other early Sunni authorities, including Ahmad ibn Hanbal (), al-Suyuti (), al-Hafiz al-Kabir, and Ibn Kathir (). The canonical Sunni collection Sunnan al-Tirmidhi reports that Muhammad limited the Ahl al-Bayt to Ali, Fatima, and their two sons when the Verse of Purification was revealed to him. In the Event of Mubahala, Muhammad is believed to have gathered these four under his cloak and referred to them as the Ahl al-Bayt, according to Shia and some Sunni sources,