speak from

speak from (something)

1. To use a part of one's body in order to speak a certain way. Try to speak from your diaphragm in order to project better during your speech. I tend to speak from my throat when I get nervous, which gives me a weak, nasally voice.
2. To talk about something from a particular position, status, or condition that lends credibility to one's words. I'm speaking from experience when I tell you that a robust investment portfolio is absolutely critical to achieve the kind of pension you desire. A lot of politicians know that what they're saying is a bunch of bunkum, but because they speak from authority the majority of people are inclined to believe them.
3. To speak or say something based on one's genuine thoughts or emotions. Typically rendered as "speak from the/one's heart" or "soul." A: "They asked me to give a speech at my father's funeral, but I really don't know what to say." B: "Just speak from the heart." You can tell she always speaks from her soul. It's one of the reasons she resonates so strongly with people.
4. To speak or say something based more off of information or knowledge, rather than one's own emotions or beliefs. Typically rendered as "speak from the/one's mind." If all you do is speak from the mind, listing facts and data points, you're never going to get your audience fully engaged with you. I can tell he's speaking from his mind whenever we get into a debate, so I'm never sure if he's saying something he truly believes in.
See also: speak
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

speak from something

to draw authority or credibility in one's speaking from something such as knowledge or experience. Believe me, I speak from experience. Listen to her. she speaks from a lot of knowledge and training.
See also: speak
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
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References in classic literature ?
I knew, too, that this was the first time in the entire history of the Negro that a member of my race had been asked to speak from the same platform with white Southern men and women on any important National occasion.
Now you speak from your heart, young man, and by digging I have reached the root of the matter.
Write out a script of your key points, but don't speak from it word for word.
Today when we say that people speak from their hearts, we mean they speak with feeling or emotion and not just abstractly or from their "heads." But in the biblical world the heart was thought of as the center of one's consciousness, the place where decisions and commitments were made.