Is it permissible to exchange moist foodstuff for its dried counterpart?
Chapter on Riba (Usury) and Exchange (Sarf)
Al-Mughni
Book of Sales
Primary text
Exchanging the moist form (rutab) for the dried form (yabis) is not permissible because the dried item is inherently deficient relative to the moist item when considering the future state. This is likened to exchanging fresh dates for dried dates.