Tawallá "Loving the Ahl al-Bayt" (Arabic: تولّى), is a part of the Twelver Shī‘ah Islām Aspects of the Religion and is derived from a Qur'anic verse.
That is of which Allah gives the good news to His servants, (to) those who believe and do good deeds. Say: I do not ask of you any reward for it but love for (my) near relatives; and whoever earns good, We give him more of good therein; surely Allah is Forgiving, Grateful.[Quran 42:23]
Furthermore, the Sunni and Shī‘ah Hadith of the Event of the Cloak is used to define who is Muḥammad's near relatives.
References
Tawalla Wikipedia(Text) CC BY-SA