It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Holy Prophet (peace and blessings be upon him) said: If any of you has a slave-girl who commits adultery and her crime is proven, then give her the punishment of lashes but do not disgrace her. Then, if she commits the same sin a third or fourth time, he said: Sell her, even if you get only a rope made of hair as her price.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 8886