"If a man takes a vow or an oath upon himself," reads Numbers 30:3, at the start of last week's Torah reading, "he shall not break his word, but all that comes from his mouth he shall do."
Broken oaths are not quite lies. A lie is a declaration against your beliefs. "From false things shall you distance yourself," reads Exodus 23:7, enjoining all forms of insincerity. Kant thought that lying is a kind of coercion. I'd add that lying offends the practice of speech itself. The liar impregnates words, by nature meant to fit the world, with an alien purpose—the intentions of the speaker against the truth.