Heard it, too.
Searched for direct Mussolini quote, but can’t find any.
He says it by inference of fascism, but not exact words.
Foriortes una (Stronger together)
Latin phrase.
It goes back 2,000 years ago.....more or less. Mussolini, I think, if you dig enough....he simply borrowed it from some Vatican guy.
"fascio di legna"
meaning "Bundle of Sticks".
And a bundle of sticks are "Stronger Together".