That’s apparently an unsourced quote but in practice it distills everything else he has to say about corporatism in particular and everything being within the state and such so whatever, just be aware you won’t be able to find a speech with that phrase in it

I would argue that it also crucially ignores his goal of taking over the power of the church as well, but Mussolini was cagey on that matter by necessity so it’s not evidence against the quote.