If you are not fit to Hold A Candle to somebody then you aren’t as good as them and shouldn’t be working in the same place. The idiom can be traced to the days when craftsmen employed unskilled labour – usually children – to hold candles to illuminate their work. It was a big insult to tell a person that they weren’t fit to “hold the candle”. It was often used as a derogatory remark to an inferior craftsman or street performer.