Lemma 29.44.8. Let $f : X \to S$ be an integral morphism. Then every point of $X$ is closed in its fibre.

Proof. See Algebra, Lemma 10.36.20. $\square$

In your comment you can use Markdown and LaTeX style mathematics (enclose it like $\pi$). A preview option is available if you wish to see how it works out (just click on the eye in the toolbar).