If they had referred it to the Messenger and to one among them who was authorized to investigate the matter, those among them who are able to draw out its meaning (yastenbitūnahu) would have known what it was. (al-Nisāʾ, 4/83) What is meant by istinbāṭ (drawing out the inner meaning) in the verse is the science of the inner (ʿilm al-bāṭin), which is Sufism (taṣawwuf). For it is well known that Sufis (mutasawwifūn) have made certain istinbāṭs from the Qur'an and the Sunnah. We shall, God willing, mention some of these later. Knowledge, the Qur'an, the hadiths of the Prophet (peace and blessings be upon him), and Islam itself all have two aspects: the outward (ẓāhir) and the inward (bāṭin). (Lumaʿ, 44)
The science of transmission and traditions (ʿilm al-riwāya wa-l-āthār) is the discipline that examines what trustworthy transmitters (thiqa) have narrated from one another. (Lumaʿ, 456)
It has also been said that the science of the outward (ʿilm al-ẓāhir) is the science of the path (ṭarīq), while the science of the inward (ʿilm al-bāṭin) is the science of the station (manzil, i.e., arrival). Again, it has been stated that the science of the inward is derived (istinbāṭ) from the outward, and that any inward (bāṭin) knowledge not supported by the outward is bāṭil (invalid, false). (Ādāb, 25)
One who is characterized by the science of the inward (that person) but does not learn the outward science in order to establish the sharia (sharia, the sacred law), and denies it, is a zindiq (heretic). His knowledge of the inward is, in reality (ḥaqīqa), not knowledge at all. It is nothing but a whispering (waswasa) that Satan has cast into him. (Furqān, 53)
The science of the inward (ʿilm al-bāṭin) is knowledge concerning the faith (īmān) of hearts (qulūb), their attainment of gnosis (maʿrifa), and their spiritual states (aḥwāl). This knowledge pertains to the inner realities of faith (īmān). This knowledge, being pure (mujarrad), is loftier than the outward knowledge related to the acts of Islam. (Furqān, 73)