The phrase "rests assured" is quite common in the English language and essentially means to be sure or confident about something. However, there are a few antonyms for this phrase that convey the opposite meaning. For instance, "in doubt," "unsure," "uncertain," "precarious," and "unsettled" all exemplify a sense of insecurity, skepticism, or unease concerning a particular situation or thing. Additionally, the phrase "rests uneasy" might be used to suggest a lack of confidence, knowledge, or trust in something. In essence, any word or phrase conveying doubt, insecurity, or mistrust is an antonym for "rests assured.