about a man who purchased a slave subject to the condition, ‘He shall be free after my death.’ He replied, ‘He is a slave whose manumission has been deferred until his owner’s death.’ Thus, he permitted a condition requiring deferred manumission, just as he permitted a condition requiring manumission. The followers of al-Shāfiʿī differed regarding such a condition, and al-Rāfiʿī deemed the view that it is invalid to be correct.

Likewise, he permitted a condition requiring the purchaser to take a slave woman as his concubine. Abū Tālib said: “I asked Ahmad about a man who purchased a slave woman on condition that he take her as his concubine, when she is a woman of distinction and her family wants him to take her as his concubine rather than use her for domestic service. He replied, ‘There is no harm in that.’”

[Since] [the seller and the slave woman] had a legitimate interest in this arrangement, he permitted it.

Likewise, he permitted the seller of a slave woman or the like to stipulate that the purchaser must not sell her to anyone other than the seller, and that if the purchaser wished to sell her, the seller could take her back for the original price. This has been reported from Umar, Ibn Masūd, and the latter’s wife Zaynab.

In sum, regarding the object of sale—which, under an unrestricted contract, is conveyed together with all its constituent parts and usufructs—the contracting parties may stipulate that it include something additional. The Prophet (peace and blessings be upon him) said: “If someone sells date palms that have already been pollinated, their fruit belongs to the seller unless the purchaser makes it a condition.” Thus, he permitted the purchaser to stipulate something beyond what an unrestricted contract would otherwise entail, and this is permissible by consensus. The contracting parties may also stipulate a reduction from it by means of a reservation, for “the Prophet (peace and blessings be upon him) prohibited reservations unless they were clearly specified.” This indicates that they are permissible when specified, just as Jābir reserved the use of his camel for riding to Medina.

As far as I know, the Muslims have unanimously agreed that it is permissible to exclude a part