Imam Husayn ‘s (a.s) had a slave who was very obedient. One day the Imam was pleased of his good services and he freed him. The slave began to weep bitterly. The Imam asked the reason. He said, “O son of Allah’s Messenger, I do not want to leave you. This slavery of mine is a thousand times better than freedom.” The Imam said, “I have freed you. Now you can live with me happily like a relative.”
One day Imam Husayn (a.s) saw a slave feeding a dog from his food. When the Imam asked him the reason he said, “O son of Allah’s Messenger. I am a trouble-stricken person, by making this dog happy I expect happiness from Allah in return.” The Imam asked him what his problem was. He said, “I am a slave of a Jew and I want freedom from him.” The Imam was moved at this slave’s yearning. He immediately came to the Jew, purchased the slave for 200 gold coins and freed him.
Reference :Akhlaq al-A’imma, Morals & Manners of the Holy Imams