preach  
verb uk/priːtʃ/ us/priːtʃ/
  (IN CHURCH)      
  [ I or T ](尤指牧师在教堂中)讲道,布道 
(especially of a priest or minister in a church) to give a religious speech
  Father Martin preached to the assembled mourners. 马丁神父向聚集的哀悼者们布道。 
 During the sermon, he preached about the need for forgiveness. 在布道中,他宣讲了宽恕的必要性。 
   (PERSUADE)      
  [ T ]竭力劝说,竭力鼓吹 
to try to persuade other people to believe in a particular belief or follow a particular way of life
  They preach the abolition of established systems but propose nothing to replace them. 他们竭力鼓吹废除现行体制,但没有提出取代方案。 
   (ADVISE)      
 [ I ] disapproving告诫;(尤指道德)说教 
to give unwanted advice, especially about moral matters, in a boring way
  He's such a pain - he's always preaching about the virtues of working hard and getting up early. 他很烦人——老在宣讲努力工作和早起的美德。 
 My mother's always preaching at/to me about keeping my room tidy. 我母亲老是告诫我保持房间整洁。 
 Idiom   
preach to the convertedidiom (also preach to the choir) 向已皈依者宣教布道;劝别人相信他们已经相信的东西
to try to persuade people to believe things that they already believe
  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。