These came from Robert A. Heinlein (1907-1988), in an essay titled, “On Writing Speculative Fiction” published in 1947. I have never read anything by Heinlein. A little research reveals he wrote science fiction, both short stories and book length. He, along with Isaac Asimov and Arthur C. Clarke, were considered the top three science fiction writers of the 40s, 50s, and 60s.
In the referenced article, Heinlein gave his rules for writing. They are:
1. You must write.
2. You must finish what you write.
3. You must refrain from rewriting, except to editorial order.
4. You must put the work on the market.
5. You must keep the work on the market until it is sold.