Custom is the Basis of Judgement: Legal Maxim 5

Legal Maxim 5

العادة محكمة

Custom is the basis of judgement

The basis for this axiom is derived from the verse: “And those who follow a way other than the path of the believers.”al-Fadani explains that what is meant by path in the verse is the path that the believers approved, and that Allah warned those who follow a different path with punishment. This indicates that it is obligatory to follow the customs of the believers. In short, the custom of the believers is the basis for judgement in the sacred law. Custom is continuously applied in fiqh. Some of the most important issues, such as determining the duration of menstruation and post-natal bleeding, return to custom. Similarly, in issues where one doubts about a small or large amount, the norm is to consider what is customarily considered large or small. 

A number of discussions fall under this legal maxim: 

When is custom established, it can be established through one occurrence alone, such as abnormal uterine bleeding, or it is established by three occurrences, or through repeated occurrences, until it is most likely that a custom is established, such as the case of training an animal to hunt. 

Custom is only considered when it is continuous and uninterrupted. A practical example of this is when a certain type of currency has become the standard currency in transactions, the default is that one must transact with the currency customarily used. The default for limits, measurements, and definitions is custom whenever the Lawgiver mentions such things without stipulating.  

And Allah knows best