It is narrated from an Ansari companion (may Allah be pleased with him) that he brought a black slave girl and said: "O Messenger of Allah! I have to free a Muslim slave. Now, if you consider this slave girl to be a believer, then free her." The Messenger of Allah (peace and blessings be upon him) asked her: "Do you testify that I am the Messenger of Allah?" She said: "Yes." The Prophet (peace and blessings be upon him) then asked: "Do you believe in resurrection after death?" She said: "Yes." The Prophet (peace and blessings be upon him) said: "Free her."