It is narrated that Imam Mahdi Ahs said, He who remembered Allah for three pahr (nine hours), was a hypocrite; he who remembered Allah for four pahr (twelve hours) was an idolater (mushrik); and he who remembered Allah for five pahr (fifteen hours) was an imperfect mumin. He, who remembered Allah for eight pahr (twenty-four hours), was a perfect momin."
Imam Mahdi's commandment was from the commandment of Allah. Allah's commandments do not change. If this practice is not there, how can there be faith (iman) and how can there be the practice of Imam Mahdi Ahs.
(Hashia Insaaf Nama - Hashia Sharif, N.6)