It was narrated that Ash-Sharid bin Suwaid Ath-Thaqafi said:

"I came to the Messenger of Allah and said: 'My mother left a will saying that a slave should be freed on her behalf. I have a Nubian slave girl; will it suffice if I free her on her behalf?' He said: 'Bring her here.' The Prophet ﷺ said to her: 'Who is your Lord?' She said: 'Allah.' He said: 'Who am I?' She said: 'The Messenger of Allah.' He said: 'Set her free , for she is a believer.'"

أَخْبَرَنَا مُوسَى بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا هِشَامُ بْنُ عَبْدِ الْمَلِكِ، قَالَ حَدَّثَنَا حَمَّادُ بْنُ سَلَمَةَ، عَنْ مُحَمَّدِ بْنِ عَمْرٍو، عَنْ أَبِي سَلَمَةَ، عَنِ الشَّرِيدِ بْنِ سُوَيْدٍ الثَّقَفِيِّ، قَالَ أَتَيْتُ رَسُولَ اللَّهِ ﷺ فَقُلْتُ إِنَّ أُمِّي أَوْصَتْ أَنْ تُعْتَقَ عَنْهَا رَقَبَةٌ وَإِنَّ عِنْدِي جَارِيَةً نُوبِيَّةً أَفَيُجْزِئُ عَنِّي أَنْ أَعْتِقَهَا عَنْهَا قَالَ " ائْتِنِي بِهَا ". فَأَتَيْتُهُ بِهَا فَقَالَ لَهَا النَّبِيُّ ﷺ " مَنْ رَبُّكِ ". قَالَتِ اللَّهُ. قَالَ " مَنْ أَنَا ". قَالَتْ أَنْتَ رَسُولُ اللَّهِ. قَالَ " فَأَعْتِقْهَا فَإِنَّهَا مُؤْمِنَةٌ ".