What is the origin of "Take what you want a pay for it"?

It’s in my head from an unknown source, and some quick googling shows several sources and alternations.

Anyone know it?

I first saw the phrase in Hercule Poirot’s Christmas, by Agatha Christie, first published in 1938. One of the characters quotes it as a Spanish proverb: “Take what you want and pay for it, says God.” Dunno if Christie just made it up for the story, or if it is a real proverb, Spanish or otherwise.

It’s rare to find something that Google doesn’t know - most say it is Spanish, another says Arabic.

I remembered where I heard it first - the Wheel of Time.

Ayn Rand used that expression, in the context of responsibility and obligation. She attributed it to an “old Spanish proverb.”

In 1920, it was presented as a Persian proverb here.