Swami Vivekananda writes in Karma Yoga: The Yoga of Action,

Do you ask anything from your children in return for what you have given them? It is your duty to work for them, and there the matter ends. In whatever you do for a particular person, a city, or a state, assume the same attitude towards it as you have towards your children—expect nothing in return. If you can invariably take the position of a giver, in which everything given by you is a free offering to the world, without any thought of return, then will your work bring you no attachment. Attachment comes only where we expect a return.