John Gill Bible Commentary

They set their mouth against the heavens,.... Against God in heaven, see Dan 4:26, against his being, saying, there is no God; against his perfections, thinking him to be such an one as themselves; against his purposes and decrees, replying against him, and charging him with insincerity, cruelty, and unrighteousness; and against his providence, either denying it, or affirming it to be unequal; and against his doctrines, ordinances, and ministers. Aben Ezra interprets it also of the angels of heaven, who are spoken against, when it is denied that there are any such beings, as were by the Sadducees; and blasphemed, when the worshipping of them is introduced. The Targum understands it of the saints of heaven, with which compare Rev 13:6 it may be applied to civil magistrates, the higher powers, who represent on earth God in heaven; and there are some that despise dominion, and speak evil of such dignities: and their tongue walketh through the earth: sparing none, high nor low, but injures all sorts of persons with their lies and calumnies. This denotes the unbridled liberty which wicked men take with their tongues; there is no restraint upon them, no stopping of them; see Psa 12:5 the universal mischief they are continually doing, and the diabolical influence of their detraction and falsehood; like Satan, their tongues walk to and fro in the earth, doing all the injury to the credit and characters of men they possibly can.