قياس
qiyās
Analogical reasoning, by which a ruling in the sources is applied to a new case sharing the same cause.
What it means
Jurists apply a ruling to a new matter when the reason for the ruling is present there too, for example the ban on wine extended to other intoxicants. It is the fourth source of law for most Sunni schools after the Quran, the Sunna and consensus. The report of Mu‘adh ibn Jabal, who said he would use his own reasoning when sources were silent, is cited as support, although its chain is discussed.