analogy; but if it departs from analogy ⦗1⦘ it counts for nothing.
Abū Muḥammad’s view was further rebutted with the argument that contracts must be construed according to the prevailing linguistic usage.
Abū al-Maʿālī al-Juwaynī said: “By custom ⦗2⦘ in al-Shāfiʿī’s statement he meant the convention that determines who shoots first, and his words are to be understood in that light, for archers commonly allow the one who puts up the stake to take the first shot.” He then added: “When the force of analogy is great and their practice diverges markedly from it, one must decisively follow analogy.”
I say: Al-Shāfiʿī’s words—may God have mercy on him—plainly show hesitation between two legal proofs. Whenever a contract is left unqualified, it is interpreted in accordance with established custom ⦗3⦘; the prevailing practice is treated as though it were an express condition, and that by itself constitutes an independent legal proof, provided the custom does not conflict with the Book of God. Analogy is also a legal proof. When analogy clashes with custom, the question arises: should analogy override the custom that functions as a condition, or should that customary “condition” take precedence over analogy, given that both are legitimate proofs?
The sounder view is that custom takes priority, because it is put on the same footing as an explicit condition—and there is no doubt that analogy is set aside in the face of a condition. According to analogy, for example, the price would be due immediately, payment would have to be made in the local currency, and the parties could dispose of the object of sale right after the contract; but all of this is abandoned once a contrary condition is stipulated.