Meat doesn't need to be washed before marinating or even cooking it.
In fact it's recommended that you don't wash any meat before marinating or cooking the meat as the bacteria and even the blood and other juices from the raw meat could spread to other things such as utensils, other foods and even surfaces.
Washing the meat won't make the food taste any better or do anything good for it.
Although for vac packed meat that is wet aged you may need to wash that meat before cooking or marinating it to remove the salt from it.
Other than that meat doesn't need to be washed prior to cooking or marinating it.