The definition of as you sow, so you shall reap is:
(proverb) if you did bad things in the past, you will get bad results in the future
if you did good things in the past, you will get good results in the future
That man was a criminal a few years ago, and now he’s in jail. As you sow, so you shall reap.
Mary was always kind to everyone. She volunteered, gave money to charity, and helped the homeless. As you sow, so you shall reap. She just won the lottery!