He smuggled into that founding document the language of Jefferson, that "all men are created equal."
what does the sentence mean? and why is it written this way? I feel it's more natural to say " He smuggled the language of Jefferson that "all men are created equal" from that founding document"
Your word order might sound more natural, but what's the context? This does have a formal sound to it, but it means the same as your version, though the preposition is 'into' suggesting that he put the idea in the document, not that he took it from the document.