Thank you for the answers!
So it does probably come from a commentary which isn’t available in digital form. I agree that it is fully consistent with Buddhadhamma, which is why I expected it to be from the Tipitaka.
But now that I think about it, the Buddha never explicitly grouped the three terms together as concepts, although he used them as if they where deeply related.
I feel extremely fortunate to have a way to learn the actual meaning of these terms, the established translations where deeply confusing for me.
Much merits to you both,
Feliks