Is it permissible for the believer to establish them, and is he commanded to do so and tasked with establishing them?

The Answer: Among what was clarified by Ibn Shu'ba—may Allah sanctify his soul—in the book (Proof of the Gnostic [Hujjat al-Arif]), he said: Allah (Glory be to Him) has no change or substitution. That which Moses brought is that which Jesus brought, and that which Muhammad brought is that which the messengers brought before.

And among what was narrated in the book (Realities of the Secrets of Religion)—a narration by Abu Muhammad Hasan ibn Shu'ba al-Harrani, the origin of which is from Ja'far ibn Muhammad al-Baqir—he said: Indeed, the lawful and the prohibited in the four laws, the variation and the incapacity, are [incumbent] upon the creature, and the cause is in the observer. All laws are one, all messengers are one. The prophets and messengers all called to the knowledge of Allah, pointed to Him, professed Him, directed to the obedience of the Ahl al-Bayt, and were eager for their guardianship [Walaya]. The "Lawful" [Halal] in all laws refers to mentioned persons whose obedience was commanded and their guardianship [Walaya]. What is lawful is lawful in its entirety until the Day of Resurrection, and what is forbidden is forbidden in its entirety until the Day of Resurrection.