to try to persuade people to believe things that they already believe

中文解释

向已皈依者宣教布道;劝别人相信他们已经相信的东西 You needn\'t bother telling us how recycling helps the environment, because you\'re preaching to the converted. 你不必费口舌告诉我们回收利用对环境有什么好处，因为我们早就知道了。