The Prophet (peace and blessings be upon him) said: "Three kinds of people are given their reward twice: a man from the People of the Book who believed in his prophet, and when he found the Prophet (peace and blessings be upon him), he believed in him too, followed him and affirmed him; for him there are two rewards. And a slave who fulfils the right of Allah Almighty and also fulfils the right of his master; for him too there are two rewards. And a man who has a slave woman, whom he brings up and brings up well, then teaches her manners and trains her well, then frees her and marries her; for him too there are two rewards."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13738
The Prophet (peace and blessings be upon him) said: "Any man who trains his slave woman and trains her well, and educates her and educates her well, then frees her and marries her, for him there are two rewards; and any slave who fulfils the right of his Lord and also fulfils the right of his master, for him too there are two rewards."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13739
The Prophet (peace and blessings be upon him) said: "When a man frees his slave woman and then marries her with a new dower, for him there are two rewards."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13740
Anas bin Malik (may Allah be pleased with him) was saying that the Prophet (peace and blessings be upon him) took Safiyyah (may Allah be pleased with her) captive, then freed her and married her. Thabit al-Bunani (may Allah have mercy on him) says: I asked Anas (may Allah be pleased with him): What was her dower? He said: Her dower was herself; he freed her and then married her.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13742
Judge Ahmad bin Muhammad al-Birti says: I asked Yahya bin Aktham about this hadith, and he said: This was specific to the Prophet (peace and blessings be upon him). The Shaykh (may Allah have mercy on him) said: This is also mentioned from al-Muzani (may Allah have mercy on him), that he mentioned this hadith to al-Shafi'i (may Allah have mercy on him), who took it as a special case. The point of the special case is that he freed her unconditionally and then married her without a dower, whereas the marriage of anyone else is never without a dower. And Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13743
Nafi' (may Allah have mercy on him) says that Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) disliked making a woman's freedom her dower until a dower was fixed for her.
The Shaykh says: The hadith of Abu Musa, in the narration of Abu Bakr bin Ayyash, indicates the same.
It has also been narrated in a weak hadith that he (the Prophet) gave her a dower.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13744
Amat Allah bint Razinah narrates from her mother that on the day of (Banu) Qurayzah and al-Nadir, he (the Prophet (peace and blessings be upon him)) brought Safiyyah (may Allah be pleased with her), leading her as a captive, until Allah granted him victory, with her arm in his hand. When she saw the captives, she said: I bear witness that there is no god but Allah and that you are the Messenger of Allah. So he (peace and blessings be upon him) let go of her arm and set her free, then proposed to her and married her, and gave her Razinah as her dower.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13745