The exoteric and the esoteric are opposites, and they are not brothers. And the proofs for that

Know, O seeker, that the Outward and the Inward are opposites (ḍiddān); they are not 'brothers' where one cannot exist without the other—as is thought by some of our brethren who have not perceived the indication behind performing the outward forms of worship.

This is supported by what came in the Book of Gnoses (Kitāb al-Maʿārif) by the 'Trustworthy Youth,' Master Abū Saʿīd [al-Maymūn] bin al-Qāsim al-Ṭabarānī, in the chapter on the prohibition of using Dissimulation (taqiyya) among believers and in private—on the authority of the Master [Imam] al-Ṣādiq—peace be upon him—in his saying to al-Mufaḍḍal bin ʿUmar—peace be upon him:

'O Mufaḍḍal, beware of performing anything of the Entities of Ruin (dhawāt al-radā).' I said: 'May I be your ransom, and what are the Entities of Ruin?' He said: 'These are the Opposites (al-ḍudūd).' I said: 'And what are these Opposites?' He said: 'That which consists of Fasting, Prayer, Pilgrimage, or Jihad; for whoever performs them [in private] as a matter of religious faith has taken another god besides Allah...'"

"He named them 'opposites' (ḍudūd) because their Outward is opposite to their Inward and vice versa, and the proof is also his saying: 'So whoever performs them—meaning their outward forms—has taken another god besides Allah.'"