You can leave your contact lenses in when you wash your face as long as you don't get any facial cleanser or soap in your eyes to make contact with the contact lenses.
The facial cleanser and soap should stay away from your eyes anyway so there should be no issue with having contact lenses in your eyes when you wash your face.
Now if you wash your hair then there could be a chance of getting shampoo in your eyes and then it could get onto the contact lenses and harm the contact lenses and may also cause eye irritation.
If you take a shower it's best to remove the contact lenses first and then put them back in after the shower.
But I've left contact lenses in my eyes when washing my face and never had any issue but if you're worried you could remove the contact lenses before washing your face.