It was not said by Cao Cao, this sentence comes from;

"The Analects of Confucius Wei Linggong": "If a worker wants to do his job well, he must first sharpen his tools. If you live in this country, you must do it. A wise man is a wise man, and he is a benevolent friend to his fellow men. ”

Definition: Tool. To do a good job, you first need to sharpen your tools. It means that to do something well, preparation is very important.

Give a simple example:

A and B both wanted to go up the mountain to chop wood, but their axes were a bit dull. A ignored it and went up the mountain with the ax because His ax is not sharp, and he only chops relatively thin wood... B is different. He brings a whetstone and sharpens the ax first. Although he starts slower than A, his preparation time I've done it well, and can chop wood very quickly. When the sun goes down, A only carries a small bundle of firewood down, but B carries a large bundle of firewood...

It can be seen that if you make good preparations, you can get twice the result with half the effort!