ValidationProvider.php

<?php

/*
* add to config/app.php providers
* App\Providers\ValidationProvider::class,
* 
* add to lang/validation.php
* 'currented' => 'The current password is not correct.',
*/

namespace App\Providers;

use Illuminate\Support\Facades\Auth;
use Illuminate\Support\Facades\Hash;
use Illuminate\Support\Facades\Validator;
use Illuminate\Support\ServiceProvider;

class ValidationProvider extends ServiceProvider
{
    /**
     * Bootstrap the application services.
     *
     * @return void
     */
    public function boot()
    {
        Validator::extend('currented',
            function($attribute, $value, $parameters, $validator) {
                return Hash::check($value, Auth::user()->password);
            }
        );

        Validator::replacer('currented',
            function($message, $attribute, $rule, $parameters) {
                return str_replace(':values', implode(', ', $parameters), $message);
            }
        );
    }

    /**
     * Register the application services.
     *
     * @return void
     */
    public function register()
    {
        //
    }
}

окей, а как теперь это вызывать внутри валидатора?

currented