Is it permissible for me to file a lawsuit to claim agricultural land that I bought with a bill of sale and witnesses, but the seller's heirs deny the sale, or is it better for me to give it up hoping for compensation from Allah?

The sale becomes binding between the two parties if its conditions are met and its impediments are absent. It is not a condition for it to be witnessed or registered in official departments. However, witnessing is desirable and registration is permissible for documentation. The land belongs to the buyer in his relationship with God if the matter is as described. As for a dispute, it requires proving the sales contract with evidence before the Sharia courts, or through concession and forgiveness. Forgiveness and concession are recommended if the buyer's soul is content with it, as Allah Almighty says: "And to pardon is nearer to righteousness. And do not forget generosity among yourselves. Indeed, Allah is Seeing of what you do." The deceased does not incur sin if he did not obstruct the process during his lifetime.