What is the legal definition of 'Tadbir' (manumission contingent upon death)?

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Tadbir signifies conditioning the manumission (freeing) of a slave upon the death of the master. This term is derived because the death occurs 'dabar' (after/following) life. The ruling is established upon Sunnah and Ijma (consensus). The Sunnah basis is the hadith narrated by Jabir, where a man manumitted his slave contingent upon his death (dabar), and when the slave was needed, the Messenger of Allah (peace be upon him) sold him to Nu'aym ibn Abdullah for eight hundred dirhams, which he paid to the owner, stating, 'You have a greater need for it.' This hadith is agreed upon (Muttafaqun 'alayh). The consensus among scholars known to Ibn al-Mundhir confirms that if someone conditions the manumission of their slave or female slave via Tadbir and does not revoke it before death, the freed person acquires liberty from the third of the estate remaining after debts and bequests are settled, provided the master was of sound legal capacity.