«وركن القياس: هو العلة»
The pillar of qiyas is the effective cause (‘illah).
«أي الوصف الذي يناط به الحكم الشرعي»
That is, the characteristic to which a legal ruling is attached.
The example of wine relates prohibition to the intoxicating property, not merely to its label. An ‘illah is a feature recognized as legally operative by appropriate evidence. Informally calling something a “reason” is not enough; the juristic cause requires support and a defensible relationship with the ruling.