Only God can save
This man knows how to plant his seeds. But he does not know how his plants grow. He does not tell his plants what they must do. But each plant grows by itself. And it continues to grow until the new seeds are ready.
It is God who causes the seeds to grow. So the man did his work. But God did the most important work.
The seed is like God‘s message. People must tell God‘s message to other people. But only God can save someone. Only God can change a person‘s life. These things are God‘s work.