en_tn/psa/073/009.md

They set their mouth against the heavens

Here "their mouth" is a metonym for their speech, and "heavens" is a metonym for God, who lives in the heavens. Alternate translation: "They speak against God, who is in the heavens" (See: rc://en/ta/man/jit/figs-metonymy)

their tongues march through the earth

The word "tongues" represents the people themselves. Possible meanings are 1) "they go through the earth saying bad things about God" or "they go everywhere and boast about themselves." (See: rc://en/ta/man/jit/figs-synecdoche)