Is it permissible to sell wheat for its derivative product, *Suwayq* (parched ground wheat)?

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The sale of wheat for *suwayq* is impermissible. This view is held by Al-Shafi'i, and it is narrated as the opinion of Malik and Abu Thawr regarding fairness in exchange, though they permitted it both equally and unequally. The prohibition rests on the basis that it is a sale of wheat for a part of itself in an unequal measure, which is disallowed, analogous to selling a *makkuk* of wheat for two *makkuk* of flour. Equality is impossible because the heat applied to one component invalidates parity, likening it to roasted grain.