“Intention is the leader of things; intention is first, they’re made by intention. If with corrupt intent you speak or act, suffering follows you, like a wheel, the ox’s foot.”

Dhammapada Verses on Speech
Every Dhammapada verse on speech — what words do, and what the well-spoken word is.
20 of 423 verses · English by Bhikkhu Sujato (CC0)
“Intention is the leader of things; intention is first, they’re made by intention. If with pure intent you speak or act, happiness follows you like a shadow that never leaves.”
“Just like a glorious flower that’s colorful but lacks fragrance; eloquent speech is fruitless for one who does not act on it.”
“Just like a glorious flower that’s both colorful and fragrant, eloquent speech is fruitful for one who acts on it.”
“Their mind is peaceful, peaceful are their speech and deeds. Such a one is at peace, rightly freed through enlightenment.”
“Don’t speak harshly, they may speak harshly back. For aggressive speech is painful, and the rod may spring back on you.”
“Not speaking ill nor doing harm; restraint in the monastic code; moderation in eating; staying in remote lodgings; commitment to the higher mind— this is the instruction of the Buddhas.”
“Speak the truth, do not be angry, and give when asked, if only a little. By these three means, you may enter the presence of the gods.”
“It’s always been this way, Atula, it’s not just today. They blame you when you’re silent, they blame you when you speak a lot, and even when you speak just right: no one in the world escapes blame.”
“Guard against ill-tempered words, be restrained in speech. Giving up bad verbal conduct, conduct yourself well in speech.”
“An attentive one is restrained in body restrained also in speech, in thought, too, they are restrained: they are restrained in every way.”
“Take anyone in this world who kills living creatures, speaks falsely, steals, commits adultery,”
“You’re not an astute scholar just because you speak a lot. One who is secure, free of enmity and fear, is said to be astute.”
“Guarded in speech, restrained in mind, doing no unskillful bodily deed. Purify these three ways of performing deeds, and win the path known to seers.”
“Restraint of the body is good; good is restraint of speech; restraint of mind is good; everywhere, restraint is good. The mendicant restrained everywhere is released from all suffering.”
“One restrained in hand and foot, and in speech, the supreme restraint; happy inside, serene, solitary, content, I call a mendicant.”
“When a mendicant of restrained mouth, thoughtful in counsel, not restless, explains the text and its meaning, their words are sweet.”
“Calm in body, calm in speech, peaceful and serene; a mendicant who’s spat out the world’s bait is said to be one at peace.”
“Who does nothing wrong by body, speech or mind, restrained in these three respects, that’s who I declare a brahmin.”
“The words they utter are polished, informative, and true, and don’t offend anyone: that’s who I declare a brahmin.”