Composer: install package directly, via command line

I need to install sofa/eloquence Laravel 5.2 package. In the documentation there is the following instruction:

1. Require the package in your composer.json:

    "require": {
        "sofa/eloquence": "~5.2", // for Laravel 5.2.*
    },

So, I guess that after requiring it in composer.json I will have to run the composer update command. But, this command will also try to update other packages that are already installed, right?

What if I don't want that, how can I install "sofa/eloquence": "~5.2" without touching anything else? For example, directly, via command line (or in any other way).

via PeraMika