The Hadith al-Thaqalayn, also known as the Hadith of the two weighty things, refers to a saying (hadith) of the Islamic prophet Muhammad. According to the hadith of the Prophet Muhammad; the Qur'an and Ahl al-Bayt ("people of the house", Muhammad's family) had been described as the two weighty things. In the context of this Hadith, Muhammad's family refers to Ali ibn Abi Talib, Fatimah bint Muhammad (the daughter of Muhammad), and their children and descendants. This hadith is accepted by Shia and Sunni Islam.
|Literal meaning||Narration of the Two Weighty Things|
The Hadith al-Thaqalayn, as most strongly established hadiths, is classified in Islam as mutawatir and the authenticity of it is confirmed by numerous chains of transmission of Shia and Sunni Muslim . According to Ayatollah Ja'far Sobhani, the hadith points the authoritative knowledge of the Ahl al-Bayt and the Quran and convinces Muslim to believe in both of them together. In spite of difference over historical interpretation, Hadith al-Thaqalayn can improve the union among the Muslims world.
According to Sunni tradition (canonical Hadith compiler Muslim b. al-Hajjaj), Hadith al-Thaqalayn was presented by Muhammad prophet at a grove called Khumm. In this tradition Yazid b.Hayyan , Husayn b.Sabrah and Umar b.Muslim went to Zayd b.Arqam, one of the transmitters of the standard Ghadir Khumm. Zayd said to them that he has "forgotten some [of what he had heard from the prophet]" but he began to recite Hadith al-Thaqalayn for them as words that heard from prophet in The event of Ghadir Khumm.
As the Allameh Tabataba'i, a philosopher and contemporary of Shia Islam, said, some points can be driven from this hadith such as "the Holy Quran will remain until the day of Judgment, the progeny of the Mohammad prophet will remain". There will not be any period of time that Shia Imam doesn't exist to guide Muslims. All the religious and intellectual needs of Muslims is supplied by pay attention to these trusts. Based on the Hadith, the authorities of knowledge and deeds belong to the household of Muhammad prophet is confirmed by him.
According to the Allameh Tabataba'i, For Shia, the people of his house turns to Ali ibn Abi Talib and his eleven descendants who were considered as Imam. This interpretation is also confirmed by Shia traditions. Ibn Abbas stated that prophet introduced his household Ali and Fatimah, Hasan ibn Ali and Husayn ibn Ali. Jabir has transmitted that the prophet has said "God placed the children of all prophets in their backbone but placed my children in the backbone of Ali".But Shia and some Sunni narrators maintain that the term household or family of the prophet refer to Ali, Fatima, and their two sons because they are the prophet’s relatives in the first degree. This belief of Shia support by Quran 3:61 -62 .
According to the Sunni tradition, It was asked from Zayd, Who are the people of his house and he answered that "His wives are among the people of his house. Also, he emphasized that the household of prophet referred to the family of Ali , the family of Aqil b.Abd al-Muttalib, the family of Jafar B.Abi Talib, and the family of Abbas [b.Abd al-Muttalib].Abu al-Qasim Abd al-Karim al-Qushayri, relates a tradition pertaining to the prophet who when asked,Who are the family of Muhammad” answered”they are every pious [Muslim]. Some writers, like Abd al-Qadir al-Jili and Muhyi al-Din Ibn Arabi, maintain the term Ahl al-Bayt referred to wives of the prophet. Aljili believed the wives of the prophet and other relatives such as the prophets uncles and their descendants. 
- Hadith Thaqalayn al-islam.org
- al-Tabataba'i, Muhammad H. Shi'ite Islam. SUNY Press. p. 180. ISBN 978-0873953900.
- Ayatollah Sobhani, Ja'far. The Doctrines of Shi'ism: A Compendium of Imami Beliefs and Practices. I.B.Tauris. p. 103. ISBN 978-1860647802.
- Dakake, Maria Massi. The Charismatic Community: Shi'ite Identity in Early Islam. SUNY Press. ISBN 978-0791470343.
- Moosa, Matti. Extremist Shiites: The Ghulat Sects. Syracuse University Press. p. 77. ISBN 978-0815624110.
- "The Book of the Merits of the Companions - Sahih Muslim - Sunnah.com - Sayings and Teachings of Prophet Muhammad (صلى الله عليه و سلم), Book 31, Hadith 5920 (in book: Book 44, Hadith 55)". sunnah.com. Retrieved 2019-08-13.