Sahih Muslim 1507
Sahih Muslim · Book 20: The Book of Emancipating Slaves · The prohibition of a manumitted slave taking anyone as a Mawla except the one who manumitted him
Jabir b. Abdullah (Allah be pleased with them) reported that Allah's Apostle (ﷺ) made it obligatory for every tribe (the payment) of blood-wit; he then also made it explicit that it is not permissible for a Muslim to make himself the ally (of the slave emancipated by another) Muslim without his permission. He (the narrator further added):
وَحَدَّثَنِي مُحَمَّدُ بْنُ رَافِعٍ ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ ، أَخْبَرَنَا ابْنُ جُرَيْجٍ ، أَخْبَرَنِي أَبُو الزُّبَيْرِ ، أَنَّهُ سَمِعَ جَابِرَ بْنَ عَبْدِ اللَّهِ ، يَقُولُ كَتَبَ النَّبِيُّ صلى الله عليه وسلم عَلَى كُلِّ بَطْنٍ عُقُولَهُ ثُمَّ كَتَبَ " أَنَّهُ لاَ يَحِلُّ لِمُسْلِمٍ أَنْ يَتَوَالَى مَوْلَى رَجُلٍ مُسْلِمٍ بِغَيْرِ إِذْنِهِ " . ثُمَّ أُخْبِرْتُ أَنَّهُ لَعَنَ فِي صَحِيفَتِهِ مَنْ فَعَلَ ذَلِكَ .
I was informed that he (the Holy Prophet) cursed the one who did that (and it was recorded) in his Sahifa (in a document).