take the cream, discard the dross (political and educational slogan); keep what is good, discard the rest; You need to be selective when studying.; In modernizing the country, don't accept uncritically all foreign ideas.
trad. 取其精華,去其糟粕
Also written 取其精華,去其糟粕【qǔ qí jīng huá , qù qí zāo pò】