Imam Ali (as): As for what Allah has made obligatory in His Book, they are the pillars of Islam, and they are five pillars. It is on these five pillars that Islam was founded, and He Almighty allocated for each of these obligatory duties four boundaries in which everyone must know. The first of them is prayer, then alms-tax (zakat), then fasting, then Hajj pilgrimage, then guardianship (wilayah), in which the latter is the seal of them and it encompasses all obligatory and recommended acts. Biḥār al-Anwār