What is the ruling on mixing wheat straw with rice or corn straw and selling it, given that the seller knows the buyer would not purchase the mixture if he knew about it, even though the mixture serves the same purpose as fodder for livestock? What are the recommendations to make the profit permissible in this case?

The seller must disclose that the hay is mixed, and it is not permissible to conceal this from the buyer, based on the Prophet's (PBUH) saying: "Whoever cheats is not one of us" and "It is not lawful for a Muslim who sells something to his brother, and it has a defect, not to disclose it to him." The seller can provide two types of hay: pure and mixed, with a difference in price, leaving the choice to the buyer.