Is Imam Al-Bukhari's Hadith: "What is wrong with people who stipulate conditions that are not in the Book of Allah? Any condition not in the Book of Allah is invalid," general or specific to loyalty to the one who emancipated a slave, and does it include every condition in transactions that makes lawful what is unlawful or makes unlawful what is lawful?

Scholars have established conditions for stipulating transactions: the condition must not contradict the essence of the contract, nor must it contradict Islamic law. They cite Ibn Hajar's narration from Al-Qurtubi: "Unlawful conditions are void, no matter how numerous," and Sheikh Al-Islam Ibn Taymiyyah's statement: "Whoever stipulates conditions in an endowment, or manumission, or a gift, or a sale, or marriage, or a lease, or a vow, or anything else, that contradict what Allah has prescribed for His servants, such that these conditions entail commanding what Allah has forbidden, or forbidding what He has commanded, or permitting what He has forbidden, or forbidding what He has permitted, then these conditions are void by the consensus of Muslims in all contracts."

The general validity of a condition that does not contradict Islamic law or the essence of the contract is supported by the hadith of Abu Hurairah from the Prophet, peace and blessings be upon him: "Muslims are bound by their conditions."

However, if a condition contradicts Islamic law or the essence of the contract, it is void, as stated by Sheikh Al-Islam Ibn Taymiyyah: "The default rule for conditions is validity and bindingness, unless evidence indicates otherwise, for the Quran and Sunnah have shown the fulfillment of contracts and covenants, and condemned treachery and breaking promises. But if the stipulated condition does not contradict the Book of Allah and His law, then it is valid. If the stipulated condition contradicts the Book of Allah and His law, then the condition is void." Scholars have differed on the ruling of a sale accompanied by a condition that contradicts the essence of the contract: does it invalidate the sale, or is the sale valid and the condition void?