"To hold your horses"

Dad: Come on kids!  Let's go!  We're going to be late.
Kid: Dad, hold your horses.

Joe: Let's go!  I don't want to miss the beginning of the movie.
Tom: Hold your horses!  I'm coming.

Meaning: "To hold your horses" is used when you tell someone to "wait" or "hold on."  People usually say "hold your horses" when they feel like the other person is being a little impatient or too much in a hurry.

 https://languagesystems.edu/