The Master of the vineyard is free to reward and give to his workers as he pleases. In his freedom to do that, the workers are freed to do their work with no fear of not receiving good things from the master. Likewise for us, we are free to work in our vocations because God has given us the Kingdom and made us partakers of it through Jesus Christ.
Image: Parable of the Workers in the Vineyard, by Meester Van Antwerpan. Public Domain. Image location: https://www.lookandlearn.com/history-images/YR0035483/Parable-of-the-workers-in-the-vineyard