Charles Ellicott Commentary Psalms 51:9

"Hide thy face from my sins, And blot out all mine iniquities." — Psalms 51:9 (ASV)

Hide your face ... — that is, your 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.