From the fact that the holy Prophet (peace be upon him and is descendants) mentioned his household alongside the holy Quran, and then called both of them as the Divine authority over his nation:

 Like the holy Quran, the words of the Prophet‟s household serve as the Divine authority, and they must adhere to them in the religious affairs. Although the Muslims were divided into two groups on the issue of Caliphate and the management of the nation‟s political affairs after the Prophet‟s demise and each of them had their own ideologies, there remains no room for any difference among them on the Ahlul-Bait (a.s) as the religious authority, because all of them agree on the validity of Thaqlayn hadith, which calls for the holy Quran and the Prophet‟s household as the source of ideology and Divine laws. It is evident that if the Islamic nations act in accordance with this hadith, their differences will be less and less, and as a result, they will reach to unity.

In his book, entitled „Sahih‟, Moslem narrates from Zeid Ibn Argham that once the Prophet (peace be upon him and his descendants) delivered a sermon next to Khum, a pool in a region between Mecca and Medina, in which he praised God and admonished the people as saying,

الا ايها الناس، فانما انا بشرٌ يوشك ان ياتي رسول ربي فاجيب و انا تارك فيكم ثقلين :

اولهما كتاب الله فيه الهدي و النور، فخذوا بكتاب الله و استمسكوا به – فحث علي كتاب الله

و رغب فيه ثم قال : و اهل بيتي، اذكركم الله في اهل بيتي ، اذكركم الله في اهل بيتي ،

اذكركم الله في اهل بيتي *

(O, people! Verily, I am a man, and soon the angel of death will come to me, and I will submit myself to his call. I leave behind two invaluable things: the Divine Book, which is the light and guidance, so adhere to it. He then went on, and my household, and my household, and my household.)

* Sahih, Moslem, vol.4, p. 1803, no. 2408