if it is a concern, such as the price being something whose preservation in the present causes harm, or if it is feared it might be destroyed or seized by usurpers, or if it will change from its current state by the time of the maturity date, then it is like someone who was not given permission. This is because the ruling of immediacy does not encompass what is passed over in silence unless it is known to be in the interest [of the principal], similar to what is explicitly stated or even more so, in which case the ruling is established via the path of indication or analogy. Whenever there is a specific concern regarding the explicitly stated condition, it is not permissible to let it lapse, nor is the ruling established in other than it. The Qadi mentioned something similar to this in another place.

Section: If he appoints him as an agent to purchase for a price in ready cash, and he purchases it on deferred payment for more than the cash price, it does not take effect for the principal. If he purchases it on deferred payment for its cash price, or for what he had specified for him, it is like the one preceding it. It is valid for the principal according to the view of the Qadi. According to what we have mentioned, it should be examined; if there is harm in it, such as being harmed by the remaining of the price with him and similar things, it is not permissible, as per our statement regarding the one preceding it. The companions of Al-Shafi'i have two views regarding the validity of the purchase.

Section: He does not have the right to sell for less than the price of a like-kind (thaman al-mithl), or for less than what he estimated for him, nor to purchase for more than the price of a like-kind, or more than what he estimated for him. Al-Shafi'i, Abu Yusuf, and Muhammad held this view. Abu Hanifa said: If he makes the agency absolute in the sale, he has the right to sell for any price whatsoever; because his wording in the permission is absolute, so it is necessary to construe it according to its absolute nature. Our argument is that it is an absolute agency in a contract of exchange, so it necessitates the price of a like-kind, just like purchasing, for he agreed to it, and what he mentioned is invalidated by [the case of] purchasing. If he sells for less than the price of a like-kind, or purchases for more than it, to an extent that people do not usually overlook (yitaghaban), or sells for less than what he estimated for him, or purchases for more than it, then his ruling is the ruling of one who was not given permission in selling and purchasing. This is the opinion of Al-Shafi'i. It is narrated from Ahmad that the sale is permissible, unlike the purchase, and the agent guarantees the deficiency; because whoever's sale is valid at the price of a like-kind, his sale is valid for less than it, like a sick person. According to this narration, the sale is valid,