It implies that your good actions will yield beneficial results. He volunteered at the shelter and later found many supporting his business. You reap what you sow.
Pro Tip 2/3
Negative Warning
It is often used to warn someone that their bad behavior will lead to negative consequences. Don't gossip about your friends, you reap what you sow.
Pro Tip 3/3
Life Choices
Reflects the idea that current choices significantly impact one's future. Choosing to save money now means a more comfortable retirement. You reap what you sow.