Charity begins at home means we can contribute to the welfare of society by our small actions. There is no need to join large groups or participate in activism, or give charities to people who claim to benefit others. We can all do it ourselves in our own small ways.
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To add to what Raimer Rainer has said, I think you would get lots of inputs on interpretations of this sentence from a google search 'charity begins at home'/ They are quite interesting. Even Yahoo Answers has a lot of replies to this question.