Having the validation messages on your site language is as easy as placing the respective language file under
Here’s an example of the validation message on the original english US version.
To get your language file start by downloading jQuery Validate zip files from here.
You will only need the language files so after you unzip the file look inside the folder dist > localization. Under this folder you’ll find a long list of language files named
messages_.min.js. Pick the one that interests you and copy the respective minified version (files ending in
min.js). Always make sure the language file matches your site language.