"Adda' bin Khalid bin Hawdhah said to me: 'Shall I not read to you a letter that the Messenger of Allah ﷺ, wrote to me?' I said: 'Yes.' So he took out a letter. In it was: 'This is what 'Adda' bin Khalid bin Hawdhah bought [from] Muhammad the Messenger of Allah ﷺ He bought from him a slave' or 'a female slave, having no ailments, nor being a runaway, not having any malicious behavior. Sold by a Muslim to a Muslim.'"  

لِي الْعَدَّاءُ بْنُ خَالِدِ بْنِ هَوْذَةَ أَلاَ نُقْرِئُكَ كِتَابًا كَتَبَهُ لِي رَسُولُ اللَّهِ ﷺ قَالَ قُلْتُ بَلَى فَأَخْرَجَ لِي كِتَابًا فَإِذَا فِيهِ هَذَا مَا اشْتَرَى الْعَدَّاءُ بْنُ خَالِدِ بْنِ هَوْذَةَ مِنْ مُحَمَّدٍ رَسُولِ اللَّهِ ﷺ اشْتَرَى مِنْهُ عَبْدًا أَوْ أَمَةً لاَ دَاءَ وَلاَ غَائِلَةَ وَلاَ خِبْثَةَ بَيْعَ الْمُسْلِمِ لِلْمُسْلِمِ  

"When anyone of you buys a slave woman let him say: 'Allahumma inni as'aluka khairaha wa khaira ma jabaltaha alaihi, wa a'udhu bika min sharriha wa sharri ma jabaltaha alaihi (O Allah, I ask You for the goodness within her and the goodness that You have made her inclined towards, and I seek refuge with You from the evil within her and the evil that You have made her inclined towards).' And he should pray for blessing. And if anyone of you buys a camel then he should take hold of its hump and pray for. blessing and say similar words."  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا اشْتَرَى أَحَدُكُمُ الْجَارِيَةَ فَلْيَقُلِ اللَّهُمَّ إِنِّي أَسْأَلُكَ خَيْرَهَا وَخَيْرَ مَا جَبَلْتَهَا عَلَيْهِ وَأَعُوذُ بِكَ مِنْ شَرِّهَا وَشَرِّ مَا جَبَلْتَهَا عَلَيْهِ وَلْيَدْعُ بِالْبَرَكَةِ وَإِذَا اشْتَرَى أَحَدُكُمْ بَعِيرًا فَلْيَأْخُذْ بِذِرْوَةِ سَنَامِهِ وَلْيَدْعُ بِالْبَرَكَةِ وَلْيَقُلْ مِثْلَ ذَلِكَ