After Macbeth kills Duncan he goes to Lady Macbeth and is concerned about not being able to say Amen. What is her advise to him?

She does not really address the not being able to say Amen because he goes right into having so much blood on his hands. She does tell him not to worry about it or it will make him mad. She tells him "A little water clears us of this deed." This advice does not prove correct later when she cannot get the blood off during her sleepwalking.