The Prophet ﷺ said, "Three persons will get their reward twice. (One is) a person who has a slave girl and he educates her properly and teaches her good manners properly (without violence) and then manumits and marries her. Such a person will get a double reward. (Another is) a believer from the people of the scriptures who has been a true believer and then he believes in the Prophet ﷺ (Muhammad). Such a person will get a double reward. (The third is) a slave who observes Allah's Rights and Obligations and is sincere to his master."  

عَنِ النَّبِيِّ ﷺ قَالَ ثَلاَثَةٌ يُؤْتَوْنَ أَجْرَهُمْ مَرَّتَيْنِ الرَّجُلُ تَكُونُ لَهُ الأَمَةُ فَيُعَلِّمُهَا فَيُحْسِنُ تَعْلِيمَهَا وَيُؤَدِّبُهَا فَيُحْسِنُ أَدَبَهَا ثُمَّ يُعْتِقُهَا فَيَتَزَوَّجُهَا فَلَهُ أَجْرَانِ وَمُؤْمِنُ أَهْلِ الْكِتَابِ الَّذِي كَانَ مُؤْمِنًا ثُمَّ آمَنَ بِالنَّبِيِّ ﷺ فَلَهُ أَجْرَانِ وَالْعَبْدُ الَّذِي يُؤَدِّي حَقَّ اللَّهِ وَيَنْصَحُ لِسَيِّدِهِ ثُمَّ قَالَ الشَّعْبِيُّ وَأَعْطَيْتُكَهَا بِغَيْرِ شَىْءٍ وَقَدْ كَانَ الرَّجُلُ يَرْحَلُ فِي أَهْوَنَ مِنْهَا إِلَى الْمَدِينَةِ