The Muslims did not free slaves as Sa'iba, but the People of the Pre-lslamic Period of Ignorance used to do so.  

إِنَّ أَهْلَ الإِسْلاَمِ لا يُسَيِّبُونَ وَإِنَّ أَهْلَ الْجَاهِلِيَّةِ كَانُوا يُسَيِّبُونَ  

ʿAisha bought Barira in order to manumit her, but her masters stipulated that her Wala' (after her death) would be for them. ʿAisha said, "O Messenger of Allah ﷺ! I have bought Barira in order to manumit her, but her masters stipulated that her Wala' will be for them." The Prophet ﷺ said, "Manumit her as the Wala is for the one who manumits (the slave)," or said, "The one who pays her price." Then ʿAisha bought and manumitted her. After that, Barira was given the choice (by the Prophet) (to stay with her husband or leave him). She said, "If he gave me so much and so much (money) I would not stay with him." (Al-Aswad added: Her husband was a free man.) The sub-narrator added: The series of the narrators of Al-Aswad's statement is incomplete. The statement of Ibn ʿAbbas, i.e., when I saw him he was a slave, is more authentic.  

أَنَّ عَائِشَةَ ؓ اشْتَرَتْ بَرِيرَةَ لِتُعْتِقَهَا وَاشْتَرَطَ أَهْلُهَا وَلاَءَهَا فَقَالَتْ يَا رَسُولَ اللَّهِ إِنِّي اشْتَرَيْتُ بَرِيرَةَ لأُعْتِقَهَا وَإِنَّ أَهْلَهَا يَشْتَرِطُونَ وَلاَءَهَا فَقَالَ أَعْتِقِيهَا فَإِنَّمَا الْوَلاَءُ لِمَنْ أَعْتَقَ أَوْ قَالَ أَعْطَى الثَّمَنَ قَالَ فَاشْتَرَتْهَا فَأَعْتَقَتْهَا قَالَ وَخُيِّرَتْ فَاخْتَارَتْ نَفْسَهَا وَقَالَتْ لَوْ أُعْطِيتُ كَذَا وَكَذَا مَا كُنْتُ مَعَهُ قَالَ الأَسْوَدُ وَكَانَ زَوْجُهَا حُرًّا قَوْلُ الأَسْوَدِ مُنْقَطِعٌ وَقَوْلُ ابْنِ عَبَّاسٍ رَأَيْتُهُ عَبْدًا أَصَحُّ