Principle Twenty-One: In the matters that revert to custom and social practice, the Qur’an’s guidance moves in step with changing times and circumstances.

This is a principle of great weight and tremendous benefit. Allah commands His servants to pursue al-maʿrūf (that which is universally recognized as good) — whose praiseworthiness is affirmed by revelation, reason, and prevailing custom — and He forbids them from al-munkar (that which is universally recognized as evil) — whose repugnance is likewise evident to revelation, reason, and custom. He also enjoined the believers to enjoin what is right and to forbid what is wrong, and He praised them for embodying that charge.

Whatever aspect of maʿrūf remains constant across all times and places—such as prayer, almsgiving, fasting, pilgrimage, and the other fixed acts of worship—Allah has commanded it at its appointed time; the obligation upon later generations is identical to that upon the first members of this community. In the same way, whatever form of munkar never changes—idolatry, unlawful killing, fornication, drinking wine, and the like—its ruling is firmly established for every age and locale; it neither alters nor differs.

The present discussion, however, concerns those matters whose rulings do vary with different regions, eras, and situations. In such cases Allah refers His servants to prevailing custom, habitual practice, and the specific interest that is manifest at that particular time.

For instance, He commands kindness to parents in both word and deed, yet He does not restrict His servants to one specific form of dutifulness, so that the command embraces every new circumstance and condition. Kindness owed to parents in one period may differ from that required in another; what is appropriate for one individual may not suit another. Hence the duty Allah has imposed is to determine the type of benevolence toward your own parents that is acknowledged in your time and your setting as genuine kindness.

The same applies to the goodness He has enjoined toward relatives, neighbors, companions, and the like. The nature, category, and individual instances of such kindness are left to what people customarily recognize as beneficence, and conversely, the forms of disrespect and harm—its opposite—are assessed accordingly.