Sayyiduna Salih bin Salih Al-Hamdani narrates from Sha’bi, he says:
I saw a man who was from Khurasan. He asked Sha’bi,“The people of our country say that whoever frees his slave-girl and then marries her, it is as if he rides a sacrificial animal.”
Sha’bi said: Abu Burdah bin Abi Musa narrated to me, from his father, that the Messenger of Allah (peace and blessings be upon him) said:
“Three types of people will have a double reward.”
One is the person from the People of the Book (i.e., a Jew or a Christian) who believed in his Prophet, then he finds my time and believes in me, follows me, and affirms me as truthful—he will have a double reward.
And one is the slave who fulfills the right of Allah and also the right of his master—he will have a double reward.
And one is the person who has a slave-girl, then he feeds her well and gives her good drink, then educates and trains her well, then frees her and marries her—he will also have a double reward.
Then Sha’bi said to the Khurasani,“Take this hadith without any effort, otherwise a person used to travel all the way to Madinah for a hadith even smaller than this.”