They have set their mouth against the heavens.
And their tongue walks through the earth. Bible see other translations

“against the heavens.” This is one way of interpreting the verse. Other scholars see it as saying that they “set their mouth in the heavens,” meaning that they speak as if they rule in heaven, and also (per the last stanza in the verse), speak as if they rule the earth. There is truth in both interpretations.

Commentary for: Psalms 73:9