In the Name of Allah, Most Merciful & Compassionate
Walaikum assalam wa rahmatullahi wa barakatuh,
Irrevocable offers are problematic in the Shariah, as the Prophetic hadiths are clear in that, “The two transacting parties have the option to cancel as long as they don’t part.” [Bukhari, Muslim, Ahmad, Abu Dawud, Tirmidhi, Nasa’i, and others–on the authority of Hakim ibn Hizam (Allah be pleased with him)]
From this, the scholars have affirmed that in any transaction the one who makes the offer has the right of revoking it before the other party accepts. [Mawsuli, Ihtiyar; Marghinani, Hidaya]
An irrevocable offer would also appear to go against the Qur’anic principle of mutual agreement at point of contract (if the seller was “forced” to sell due to this kind of offer). Allah Most High says, “Believers, do not consume each others‘ wealth in wrongful ways; rather, let it be through dealings on the basis of mutual agreement.” [Qur’an, 4.29]
However, if it is the law of the land, then a Muslim would be bound to uphold it–and then it wouldn’t corrupt the contract (though it would remain wrong for a Muslim themselves to offer or demand it). [Based on the legal opinion of fuqaha’ of verification, such as Mufti Mahmoud Ashraf Usmani, and others, on related issues.]
And Allah alone gives success.
