Is it permissible for the first partner to claim against the second partner and request a reconsideration of the distribution that took place between them by virtue of a preliminary agreement to dissolve the partnership, and does the rule "The two parties to a transaction have the choice as long as they have not separated" apply to this case? And what is the ruling if the second partner agrees to reconsider, then passes away, and the heirs refuse that?

If two partners agree to divide their company between them, and each chooses a part and they separate on that basis, the division is not invalidated by a claim of fraud (ghabn) in it, because it is akin to a sale. The fact that some of what one partner chose includes debts does not affect the division, as these are part of mixed assets, similar to selling an heir's share in an inheritance. If the two partners agree to annul the first division and conclude a second division and separate on that basis, the heirs cannot revoke it. However, if what occurred from the second partner was merely a promise to reconsider the first division, and the partner died before fulfilling the promise, the heirs have the option to enforce or not enforce this promise.