The wonderful gift of speech God has given us should be used for His glory, and should not be taken for granted or abused. The tongue should be used for the right purposes, but many times Satan gets hold of it and the results are devastating. More damage is probably done by the tongue in lives, homes, and churches than by any other means. Sometimes it is only covering sin in the heart, as was the case with Ananias and Sapphira, as related in Acts 5. Truth alone is eternal, but liars will be revealed and judged in the last day.
Lips can only utter words, but the deceit of lies comes forth from the heart.
If the intent of the heart is evil, then evil statements will come forth from the lips. This is so emphatic that it is repeated twice in these verses.