1021 B
Their ... Their
The word "their" refers to the "Jews and Greeks" of Romans 3:9.
Their throat is an open grave
The word "throat" is a metonym for everything that people say that is unrighteous and disgusting. Here "open grave" is a metaphor that refers to the stench of the evil words of the people. (See: rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/figs-metaphor)
Their tongues have deceived
The word "tongues" is a metonym for the false words that people speak. Alternate translation: "People speak lies" (See: rc://en/ta/man/translate/figs-metonymy)
The poison of snakes is under their lips
Here "poison of snakes" is a metaphor that is used to represent the great harm of the evil words that the people speak. The word "lips" refers to the words of the people. Alternate translation: "Their evil words injure people just like the poison of a venomous snake" (See: rc://en/ta/man/translate/figs-metaphor and rc://en/ta/man/translate/figs-metonymy)