Muwatta 2241

Malik said: the agreed practice among us regarding a slave whose master frees a portion of him, a third, a quarter, a half or a share, after the master's death: only the portion the master freed and named is freed. That is because the manumission of that portion became due only after the dead man's death, while his master was entitled to choose so long as he lived. When the manumission fell on the slave by the testator, the testator had only what he took from his property, and the remainder of the slave was not freed, because his property had passed to someone else. Unless he bequeaths that the rest of the slave be freed from his property, in which case it binds his partners and heirs. ¹

Belongs to the Muwatta, Book of Manumission and Clientage. Source: the Muwatta. Mentions Malik ibn Anas. Built on in the chapters on manumission (itq) and bequest (wasiyya).