>>512044842
It's from an article/interview in 1930, pic related, it's a key point he re-iterated many times over the years in various interviews.

The earliest I know of his his interview with Viereck in 1923.

https://famous-trials.com/hitler/2529-1923-interview-with-adolf-hitler

Again in 1932.

https://alphahistory.com/nazigermany/hitler-nazi-form-of-socialism-1932