What is the ruling on selling agricultural land for the purpose of recovering money, if building on it is prohibited due to disobeying the ruler, and is the seller sinful if he knows that the buyer will build on it, and will the money resulting from the sale be unlawful?

If prohibiting construction on agricultural land is not for a public interest, then it is permissible to sell the land to someone who will build on it, and violating this prohibition is not a sin. However, if the prohibition is for a public interest, then it is not permissible to sell the land to someone who is known or suspected to build on it, because that would be assisting in sin; as Muhammad Mawlud said in Al-Kafaf: "And everything with which the buyer intends a sin, its sale to him is forbidden." If the seller does not know the buyer's intention to build on it, then doubt is not considered.