Charles Ellicott Commentary Psalms 73:9

"They have set their mouth in the heavens, And their tongue walketh through the earth." — Psalms 73:9 (ASV)

They set. —The last clause is repeated here using a more defined image:

“They have set their mouth in [not against] the heavens,
While their tongue walketh through the earth.”

An image very expressive of a towering pride, boasting itself to the skies, and trumpeting its own praises through the world.