Three words organise much of Sufi writing about how outward and inward religion relate. Sharīʿa (shar, shariat) is the sacred Law. Ṭarīqa is the path of the seeker, the method by which he travels. Ḥaqīqa is the Truth or Reality at the end of it. Nicholson gives the framework in a single sentence:
The Sūfī who sets out to seek God calls himself a ‘traveller’ (sālik); he advances by slow ‘stages’ (maqāmāt) along a ‘path’ (tarīqat) to the goal of union with Reality (fanā fi ’l-Haqq).
In the Awārif’s glossary these are also types of person: ahl-i-shariat (“one of the shar’”), ahl-i-tarikat (“one of the Path (to God)”), ahl-i-hakikat (“one of truth”). (Introduction)
The most quoted treatment is al-Hujwīrī’s, given in Nicholson’s chapter on the Gnosis:
“The Law without the Truth,” says Hujwīrī, “is ostentation, and the Truth without the Law is hypocrisy. Their mutual relation may be compared to that of body and spirit: when the spirit departs from the body, the living body becomes a corpse, and the spirit vanishes like wind. The Moslem profession of faith includes both: the words, ‘There is no god but Allah,’ are the Truth, and the words, ‘Mohammed is the apostle of Allah,’ are the Law; any one who denies the Truth is an infidel, and any one who rejects the Law is a heretic.”
He says the same thing in the Kashf’s first chapter, in the vocabulary of outward and inward: “The outward and inward aspects cannot be divorced. The exoteric aspect of Truth without the esoteric is hypocrisy, and the esoteric without the exoteric is heresy. So, with regard to the Law, mere formality is defective, while mere spirituality is vain.” (Chapter I) And at the close of his chapter on Ṣūfiism he states that anyone who denies the substance of the path denies “the whole Sacred Law of the Apostle.” (Chapter III) The Awārif’s introduction makes the same claim in terms of the people: “They find that the tarikat (of the darvish) and the shari’at (of Islam) agree; and that whoever is imperfect in shari’at is also imperfect in hakikat (truth).”
Nicholson also gives the harder case, in which the advanced gnostic is said to stand above the Law. He puts the argument in the mystics’ own voice:
The mystic Unitarians admit the appearance of contradiction, but deny its reality. “The Law and the Truth” (they might say) “are the same thing in different aspects. The Law is for you, the Truth for us. In addressing you we speak according to the measure of your understanding, since what is meat for gnostics is poison to the uninitiated, and the highest mysteries ought to be jealously guarded from profane ears.”
His own comment is a caution. “It must be borne in mind that this is a theory of perfection,” he writes, and in practice, “of course, it leads in many instances to antinomianism and libertinism, as among the Bektāshīs and other orders of the so-called ‘lawless’ dervishes.” Al-Hujwīrī draws the same line at the other end. In his survey of the twelve sects of Sufis, ten are approved and two condemned, and of the second, the Ḥallājīs, he says they “have abandoned the sacred law and have adopted heresy.” (Chapter XI) The tradition thus holds both claims together: the Truth is the point of the Law, and the Law is the safeguard of the Truth.
For the claim of blame made without the law, see the Malāma entry; for the stages of the path, Ḥāl and Maqām; and for the goal, Tawḥīd and Ḥulūl and Ittiḥād.
The passages above are quoted from complete public-domain translations, all of which are free to read here in full.
Read the Kashf al-MaḥjūbRead The Mystics of IslamRead the Awārif al-Maʿārif