But why? If you have a commit, then you already have these changes applied to your files. Some files may have changed since the commit, but then if you try to get a quote for these commit changes, then stash will be the difference between your current files and the state of these files when commit. I'm trying to say that I can’t come up with a case when you need it.
But in any case, you can get the commit changes, create a diff, apply it, and then save everything that was different.
git diff YOUR-COMMIT^ YOUR-COMMIT > stash.diff
git apply stash.diff
git commit .
git stash
stash.diff. git diff git apply.