The first prerequisite in the exegesis of the Qur`an is that the commentator must have a complete knowledge of the rules of Arabic grammar so that under the shadow of this comprehensive knowledge, he is able to clearly differentiate the ‘the subject of a verb’ (ألفاعل) from the ‘the object of a verb’ (ألـمفعول); the ‘adverb’ (ألظرف) from the ‘qualified verb’ (ألمظروف); the ‘denotative of state’ (ألحل) from the ‘subject of state’ (ذو الحال); and the ‘coupled’ (ألـمعطوف) from the ‘antecedent’ (ألـمعطوف عليه).
However it is not only in understanding the Qur`an for which this sort of a key is needed. Rather, in order to benefit from a book in any language, a person must possess knowledge of the rules of grammar of that particular language. How many times has it been seen that without knowing the rules of Arabic grammar, many errors in the understanding of the meaning of a verse of the Qur`an take form.
This first condition is so clear that there is no need to go further in the discussion of this point.
However we should mention that being aware of the rules of Arabic grammar does not mean that a person must be a specialist in the rules of the sciences of: derivation, declension of words and syntax of sentences, since it is not necessary to be an expert in these fields to be a commentator of the Qur`an. Rather, it is sufficient that a person has a general understanding of these sciences, through which he would be able to understand and point out the various differences (in the words). Such a form of understanding (of the rules of Arabic grammar) can be attained by going through an entire course in the fields of the science of derivation (of the words) and the science of syntax of sentences.