Hide thy face ... — i.e., thy angry look. (See Psalms 21:9.) More usually the expression is used in the opposite sense of hiding the gracious look. As long as Jehovah kept the offences before Him the breach in the covenant must continue.
Related Commentaries of Psalms 51:9
Psalms 51:9
9 Hide thy face from my sins, and blot out all mine iniquities.