Nafi' (may Allah have mercy on him) says that a slave who was from the khumus forced himself upon a slave girl who was from the same khumus, so Sayyiduna Umar (may Allah be pleased with him) flogged him and banished him, and did not punish the slave girl at all.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحدود / 17049