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)
وَقَالَ مَنْ تَوَلَّى قَوْمًا بِغَيْرِ إِذْنِ مَوَالِيهِ فَعَلَيْهِ لَعْنَةُ اللهِوَالْمَلَائِكَةِ لَا يَقْبَلُ اللهُ مِنْهُ صَرْفًا وَلَا عَدْلًا