Imam al-Shafi'i (may Allah have mercy on him) says: I heard this hadith from Sufyan (may Allah have mercy on him) very many times, more than I can count. He would not mention the reduction of the price in it, and would add nothing beyond that the Prophet (peace and blessings be upon him) "forbade selling fruits for years ahead"; then after that he added that he (peace and blessings be upon him) "ordered that the price be reduced on account of drought."
(b) Sufyan (may Allah have mercy on him) says that after the sale for years and before the reduction of the price for calamity, Humayd (may Allah have mercy on him) used to mention some words which I did not remember, so I would refrain from mentioning the reduction of the price, because I did not know what those words were, although the hadith contains the order to reduce the price for calamities. Imam al-Shafi'i (may Allah have mercy on him) says: It may be that the words of Humayd's hadith which Sufyan (may Allah have mercy on him) did not remember indicate that his (peace and blessings be upon him) order to reduce the price is like his order to settle on half, or his order to give voluntary charity, an encouragement towards good, not an obligation, or something similar; and something else is also possible.
Since the hadith carries both meanings, and there is no indication in it of which of the two is more fitting, it is not permissible in our view, and Allah knows best, to rule against people in their wealth that they must give up what is due to them, without an established report that it be given up.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10629