Is it valid to exchange two varieties of differing value of one genus for a single variety of that same genus?

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The transaction where two different varieties of differing value from one genus are exchanged for a single variety of that same genus is valid. This applies, for example, exchanging a Moroccan Dinar and a Saburi Dinar for two Moroccan Dinars, or a sound Dinar and a Qirad Dinar for two sound Dinars, or two Qirad Dinars, or red and brown wheat for white wheat, or Barnī and Muqallī dates for Ibrahimi dates. This position is held by Malik and Al-Shafi'i, based on the principle that the price must be apportioned to its counter-value according to their difference in value. The evidence for permissibility is derived from the Prophet's saying: 'Gold for gold, like for like, and silver for silver, like for like.' This indicates that the sale is permissible when the observed equivalence exists, which is equivalence in weight for weighed goods and in measure for measured goods. Furthermore, quality is disregarded in matters of riba when one genus is exchanged for its own genus, which applies even if the types differ, just as if the types were the same. The difference in value is contingent upon quality and inferiority; since gold of equal weight is sold for gold, it is valid, just as if the type agreed. Apportionment of the counter-value to the compensated item occurs only when it includes two genera or in non-riba items, evidenced by the case where one variety is sold for a variety containing good and poor quality.