By His Bootstraps

One of my favorite Heinlein stories:

“By His Bootstraps” is a science fiction short story by Robert A. Heinlein that plays with some of the inherent paradoxes that would be caused by time travel. It was originally published in the October 1941 issue of Astounding Science Fiction under the pen name Anson MacDonald. It was reprinted in Heinlein’s 1959 collection, The Menace From Earth.

The story is available here (links to pdf)