LF, I don’t think there’s a pasuk anywhere with the words the OP used in his title. I think he was trying to quote the pasuk from Va’eschanan,
“V’Nishmartem me’od le’nafshoseichem…”
In the context of that pasuk, the words are not instructing to watch our physical bodies.
Can someone explain how we came to use these words to learn that we have to stay safe / stay healthy?
And can flatbusher tell us what he was quoting?