Imam Zainul Abideen (a.s) was extremely kind and affectionate towards slaves and slave girls. He used to take very less work from them for his personal needs. One day a slave girl began to weep after hearing about the incidents of Karbala’ from him. When the Imam saw this devotion of hers, he said, “Go, I have freed you for the sake of Allah.” She said, “O son of Allah’s Messenger (S), I will continue to remain in your service. Being at your feet is everlasting happiness for me.”
Tawus Yamani says that he saw Imam Zainul Abideen (a.s) surrounded by his slaves and slave girls. He was telling them, “I have forgive your mistakes. You all pray to Allah that He forgives the mistakes of Ali Ibnul Husayn .”
Reference :Akhlaq al-A’imma, Morals & Manners of the Holy Imams