Ubaydullah bin Abdullah bin Utbah bin Mas'ud (may Allah have mercy on him) says that a man of the Ansar came to the Prophet (peace and blessings be upon him) with his black slave girl and said: O Messenger of Allah (peace and blessings be upon him)! I owe the freeing of a believing neck (slave); shall I free this one? He (peace and blessings be upon him) asked the slave girl: "Do you bear witness that there is no god but Allah?" The slave girl said: Yes. He (peace and blessings be upon him) asked: "Do you bear witness that Muhammad (peace and blessings be upon him) is the Messenger of Allah?" The slave girl answered yes. He (peace and blessings be upon him) asked: "Are you certain of being raised after death?" She said: Yes. He (peace and blessings be upon him) said: "Free her."
This is mursal, and it has already passed with a connected chain (mawsul) with part of its meaning.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الظهار / 15271