Masruq narrates from Sayyiduna Abdullah (may Allah be pleased with him) that a slave woman should not be married while there is a free wife, except that a slave (man) may do so. Abu Abdullah conveyed it by ijazah (licence) from Abu al-Walid.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14011