Al-Hasan (may Allah have mercy on him) said: The mukatab may free (a slave) and give a gift only with the permission of his master. In the hadith of Muhammad bin Abi Adi (may Allah have mercy on him) it is: The mukatab may free (a slave) and give a gift only with the permission of his master.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21718