It is narrated from Hasan (may Allah have mercy on him): A man makes various bequests, among which is the freeing of a slave, and if that bequest exceeds one third (of the estate), then the slave will be freed first.
Hadith Referenceسنن دارمي / من كتاب الوصايا / 3259
It is narrated from Ata that if a person makes a will and frees (a slave), and there is 'awl' (i.e., the shares are more than the estate) in his will, then this 'awl' will apply to all those involved in the freedom and the will. Ata said: The people of Madinah have prevailed over us in this matter; they begin with freedom (of the slave).
Hadith Referenceسنن دارمي / من كتاب الوصايا / 3261
Amr bin Dinar said: If a man makes a bequest to free (a slave) and makes another bequest that exceeds one third, then the shares will be distributed from (only) one third.
Hadith Referenceسنن دارمي / من كتاب الوصايا / 3262
Hasan (may Allah have mercy on him) said: If a man makes a bequest of more than one third of his wealth, in which there is also the emancipation of a slave, he said: Emancipation will take precedence.
Hadith Referenceسنن دارمي / من كتاب الوصايا / 3263