The Supreme Buddha taught us the merits of protecting the precepts as follows:

Virtuous person will grow in wealth by protecting his precepts.
His virtuous life will promote his good name among people.
With one’s cultivated virtue, one becomes courageous to go and work among any kind of crowd.
By the time a virtuous person dies, he will be able to face the death with a good mindfulness.
Once he died, he will be born in an upper level world like heaven.

Furthermore, a virtuous person can get many merits as a result of his effort on protecting the precepts.