Then Jesus said to the crowds and to his disciples, “The scribes and the Pharisees sit on Moses’ seat, so do and observe whatever they tell you, but not the works they do. For they preach, but do not practice.”
I can only assume that the phrase “practice what you preach” could be tied to this verse. As a child, the church we went to left me with the impression that the pastor lived a sin free life. There was no real life examples used during his preaching. That’s why a appreciate a pastor who uses himself as a bad example of following Jesus, it shows his humanity and gives church goers practical examples of how the bible is reflected in how we live. None of us will ever be perfect, but we can use what we learn through God’s word to our best.