The phrase ‘Practice What You Preach’ means to behave the way you tell other people to behave.
Example of Use: “Other countries need to see that we practice what we preach when it comes to human rights.”
Like so many statements, the origin of the idiom 'practice what you preach' is the Bible. The saying is found in Matthew 23:3 and reads thusly: “So you must obey them and do everything they tell you. But do not do what they do, for they do not practice what they preach.”