Practise what you preach
Definition 1 of 1
Pro Tip 1/3Credibility Importance
Using the phrase emphasizes the importance of integrity and trustworthiness in one's actions. 
A dietitian who eats healthily is practising what she preaches.
Pro Tip 2/3Not for Instructions
The phrase is not used for simple instructions, but for moral or ethical advice. 
If you tell your friends to recycle, make sure you practise what you preach.
Pro Tip 3/3Social Expectations
It touches on societal expectations where leaders or role models are involved. 
The community leader practises what he preaches by volunteering weekly.