Commentary for Pesachim 80:17

There was a certain boat carrying wheat, which capsized before Passover in the Ḥishta River. Rava permitted its owners to sell the recovered grain to gentiles during Passover. Rabba bar Levai raised an objection to the opinion of Rava from a Baraita: With regard to a garment in which diverse kinds, a prohibited mixture of wool and linen, has been lost, i.e., a wool garment into which a linen thread was sewn or vice versa, one may not sell it to a gentile; and one may not even fashion it into a saddlecloth for a donkey. It is prohibited to do so lest one remove a piece of this garment and sew it onto his own clothing. However, one may fashion it into a shroud for a dead body, as there is no concern that he will remove it from the dead. What is the reason that one may not sell it to a gentile? Because of the concern that the gentile will resell it to a Jew. It should therefore be prohibited to sell this wheat to gentiles, lest they resell it to Jews. Rava reconsidered and then said: He should sell this wheat one kav at a time, i.e., in small measures, each to a different Jew, but not to any one Jew in large quantities, so that all of this wheat will be used before Passover. And Rabenu Ephraim asked: why is the wheat prohibited, it has not split? And he answered, normal soaking of wheat cannot become chametz unless the wheat grains split. But this wheat even though it is smooth since they lie in water for a long time then can become chametz.