Abu al-Sha'tha (may Allah have mercy on him) said that marrying slave women is not permissible nowadays, because one has the means to marry free women.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13997
Hadith Gradingمحدثین:صحيح
Hadith Takhrij«صحيح۔ اخرجه الشافعي في الام 4/ 301»