Al-Kāfi - Volume 5 > Marriage of a Free Man with a Slave
Hadith #7

7- مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ ابْنِ فَضَّالٍ عَنِ ابْنِ بُكَيْرٍ عَنْ بَعْضِ أَصْحَابِنَا عَنْ أَبِي عَبْدِ اللهِ (عَلَيْهِ السَّلام) قَالَ لا يَنْبَغِي أَنْ يَتَزَوَّجَ الرَّجُلُ الْحُرُّ الْمَمْلُوكَةَ الْيَوْمَ إِنَّمَا كَانَ ذَلِكَ حَيْثُ قَالَ اللهُ عَزَّ وَجَلَّ وَمَنْ لَمْ يَسْتَطِعْ مِنْكُمْ طَوْلا وَالطَّوْلُ الْمَهْرُ وَمَهْرُ الْحُرَّةِ الْيَوْمَ مَهْرُ الأمَةِ أَوْ أَقَلُّ.

7. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from ibn Faddal from ibn Bukayr from certain persons of our people who have said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said, ‘It is not proper today for a free man to marry a slave- girl. It was permissible as Allah, most Majestic, most Glorious, has said, ‘If one cannot find resources. . . .’ (4:25) Resources is a reference to mahr (dower). Today mahr (dower) is like the mahr (dower) of slave-girls or less.’”