How do I find all files containing specific text within the file on Linux?

I'm trying to find a way to scan my entire Linux system for all files containing a specific string of text.
I'm looking for text within the file, not in the file name.

When I was looking up how to do this, I came across this solution twice:

find / -type f -exec grep -H 'text-to-find-here' {} \;

However, it doesn't work. It seems to display every single file in the system.

Is this close to the proper way to do it? If not, how should I?