Thi is a common parenting advice. Your children will follow what you do, not what you say. This applies to others too.
Here’s a cool demonstration done by Zig Ziglar.
He told his audience that he will say “1, 2, 3, Go”. When he says “Go”, the audience had to clap.
Then he proceeded to say “1,2,3” and then he clapped. Most people clapped along with him. then he proceeded on to say “Go”. then some people clapped again. It was funny and a proof of his point.