The difference however between the Qur`an and man made laws...
The difference however between the Qur`an and man made laws is that whereas the reason in separating the points of enlightenment from the original law in the case of the latter is the limitation of human awareness which requires annotations, exceptions and additions over time. In the Divine legal system, such limitation does not arise, and all the details of a law - whether those which are to be outdated or added in the future - are clear for a Law Maker like Allah (awj).
Nevertheless sometimes social interests necessitate that the specifics of the laws be expounded gradually, and not all at one place. For example, the Qur`an has prohibited the taking of interest and has stated: .وَ حَرَّمَ الرِّبٌوا... “And He (Allah) has prohibited interest.” [^1] However, in the ahadith, we observe that in some circumstances, interest is permissible.
For example: interest between a father and son or a husband and wife, and the benefits of such exceptions are completely clear, for in these examples, due to the uniformity of the kitty and the close relationship of both parties, interest does not bear an oppressive color and has thus been designated as lawful.
Thus, if a commentator of the Qur`an wants to explain such verses of the Qur`an – whose number is not small – and was to rely solely on the verses of the Qur`an, and was to abstain from referring to the ahadith, then he would have acted against the verse of the Qur`an quoted above and in essence, would have neglected this verse of the Qur`an!
The need to explain and elucidate some of the verses of the Qur`an which deal with the practical laws of Islam (whether the general import of their meanings such as salat, zakat, etc. or exceptions and limitations, i.e. the points of enlightenment and exceptions in law) by way of the sunnah and ahadith, led the Fuqaha (Jurisprudents) to expound such verses separately, and write books that specifically concern such kind of verses.
The best works and exegeses of this nature on the ayat al-ahkam are of al-Jassas, Fadil al-Miqdad, Muhaqqiq Ardibili and al-Jazairi.