Malik Muwatta Book 54, Number 54.16.42:


Malik related to me from his paternal uncle, Abu Suhayl ibn Malik, that his father heard Uthman ibn Affan say in a khutba, "Do not oblige the slave-girl to earn money unless she has a skill. When you oblige her to do that, she will earn money by prostitution. Do not oblige the child to earn money. If he does not find it, he will steal. Have integrity since Allah has integrity with you, and you must feed them good food."