if a man becomes the client of any people without the permission of his patrons (i.e. those who have freed him), on him will be the curse of Allah, of angels and of all people; no obligatory or supererogatory worship will be accepted from him. (Using translation from Abū Dāʾūd 5114)
عَنِ النَّبِيِّ ﷺ مَنْ تَوَلَّى قَوْمًا بِغَيْرِ إِذْنِ مَوَالِيهِ فَعَلَيْهِ لَعْنَةُ اللهِ وَالْمَلَائِكَةِ وَالنَّاسِ أَجْمَعِينَ لَا يُقْبَلُ مِنْهُ يَوْمَ الْقِيَامَةِ عَدْلٌ وَلَا صَرْفٌ