Example: I sell you this car on the stipulation that I may travel in it to Mecca. This stipulation is made within the contract itself, and it is valid.
Another example: I sell you this car, and after the contract has been concluded through offer and acceptance, I say, “I stipulate that I may travel in it to Mecca.” This is valid, because it is made during the period of the option. If you were to say, “No,” I would say, “I have now rescinded the sale,” because the option remains in my hands as long as we have not yet parted; thus, we may add a stipulation.
Another example: I sell you this car, retaining the option for three days. On the second day, I come to you and say, “I stipulate that I may travel in it to Mecca.” This is valid, because it is made during the period of the two options.
As for an agreement made before that—that is, what the parties agreed upon before the contract—the established position in the madhhab is that it is not legally effective.
For example, you and I agree that I will sell you the car, on the stipulation that I may travel in it to Mecca. Then, when concluding the contract, we do not mention this stipulation, either because we forgot or because we relied on what had previously been agreed. Is this stipulation considered effective or not? The answer, according to the madhhab, is that it is not considered effective.
The correct view, however, is that it is considered effective, for the following reasons:
First: because of the general meaning of the hadith: “Muslims are bound by their stipulations” (1), and I
(1) Al-Bukhari cited it in suspended form with a decisive wording in al-Ijarah, “Chapter: The Fee of Brokerage.” It was transmitted with a connected chain by Ahmad and Abu Dawud in al-Qada, “Chapter: Concerning Reconciliation” (3594), and by al-Hakim (2/49), on the authority of Abu Hurayrah, may Allah be pleased with him.
Al-Tirmidhi also narrated it in al-Ahkam, “Chapter: What Has Been Reported from the Messenger of Allah concerning Reconciliation between People” (1352), through Kathir ibn Abdullah al-Muzani, from his father, from his grandfather, who reported that the Messenger of Allah said: “Reconciliation is permissible between Muslims, except a reconciliation that makes lawful what is unlawful or makes unlawful what is lawful. Muslims are bound by their conditions, except a condition that makes lawful what is unlawful or makes unlawful what is lawful.” He said: “Hasan sahih.” Kathir ibn Abdullah in its chain was declared weak by Ahmad and Ibn Ma'in; see Tahdhib al-Sunan (5/213).
The hadith has a supporting narration from Aishah and Anas, may Allah be pleased with them, recorded by al-Daraqutni (3/27-28) and al-Hakim (2/49-50), with the wording: “Muslims are bound by their conditions so long as they conform to the truth.” However, its chain is weak, as al-Hafiz stated in al-Talkhis (1195). He also related that Ibn Hazm and Abd al-Haqq declared the hadith weak, and Ibn al-Qattan likewise judged it weak in Bayan al-Wahm wa al-Iham (1299). Those who graded it authentic did so in view of its multiple chains. Allah knows best. See al-Irwa (5/142).