Bava Batra 150B

אמר ליה: אנן ⁠– משום דלאו כרות גיטא מתנינן לה.

Rav Ashi said to Ravina: The reason the slave is not emancipated if the master reserved part of the property for himself is not that the slave is included in the property that the owner reserved for himself. Rather, we teach this halakha as being due to the fact that the document is not a bill of manumission that completely severs the bond between the slave and the master.

אמר רבא אמר רב נחמן: חמשה עד שיכתבו כל נכסיהם; ואלו הן: שכיב מרע, עבדו, אשתו, ובניו, מברחת.

§ Rava says that Rav Naḥman says: There are 5 types of gifts to which specific halakhot apply, but the halakhot do not apply until the owners write a deed granting all of their property to another without reserving anything for themselves, and they are as follows: The gift of a person on his deathbed, a gift to one’s Canaanite slave, a gift to one’s wife, a gift to one’s sons, and the gift of a woman who shelters her property from her prospective husband by transferring her property to another before her marriage. In this latter case the rabbis instituted that if her husband dies or divorces her she can reclaim the property.

שכיב מרע ⁠– דתנן: שכיב מרע שכתב כל נכסיו לאחרים, ושייר קרקע כל שהוא ⁠– מתנתו קיימת; לא שייר קרקע כל שהוא ⁠– אין מתנתו קיימת.

The Talmud explains each of these cases: In the case of a gift of a person on his deathbed, this is as we learned in the Mishnah (146b): With regard to a person on his deathbed who wrote a deed granting all of his property to others, and he reserved for himself any amount of land, his gift stands even if he subsequently recovers. If he did not reserve for himself any amount of land, and he recovered, his gift does not stand, as the gift was conditional upon his death, since evidently he did not intend to leave himself without means of support if he survived.