Marinating adds flavor and tenderizes meat, but it does not kill bacteria.
For this reason, marinate meat only in the refrigerator to keep it at a
temperature where bacteria won’t grow.
Cooking the meat to a safe temperature will often kill bacteria that may have been in the meat. If the marinating meat contained bacteria, it would pass to the marinade. Therefore, never save and re-use marinade, and never use marinade on cooked meat unless the marinade has been brought to a boil.