《资治通鉴·宋纪·宋纪十五》
人在监狱中受到痛苦，就会全心向善，所以聪明的人把监狱当作磨炼的场所。朕特别使犯人受一点苦楚，希望他们悔过自新，然后再对他们宽恕！ 
夫人幽苦则思善，故智者以囹圄为福堂，朕特苦之，欲其改悔而加矜恕尔。 
When people are suffering in prison, they will wholeheartedly do good, so the clever people treat prison as a place of tempering. I specially make criminals suffer a little bit so that they repent and reform, and then forgive them!