According to Mayo Clinic leftovers can be kept for three to four days in the refrigerator. Be sure to eat them within that time. After that, the risk of food poisoning increases. It is recommended to freeze leftovers immediately if you don't think you'll be able to eat them within four days.
When you're ready to eat leftovers, reheat them on the stove, in the oven or in the microwave until the internal temperature reaches 165 F (74 C).
To help keep refrigerated foods from spoiling or becoming dangerous to eat, you can follow the safe storage time limits shared by What's Cooking America.
Are you storing food safely? Find food storage tips at U.S. Food and Drug Administration.