Lumen API leaves password field blank in database

I am using Lumen framework to create an API. I created the UserController.php to validate my user's email and password. In the User Model, I declared the password, create_at and updated_at fields as hidden and id, email_id and name field as fillable. When I do a post call to the API, my email and password are validated properly (if I dont send a password, the API throws an error message as expected) but in the back-end database, the password field is left empty but an entry is created for the user for all the other fields including timestamps. Although when I add the password field to the fillable variable, the hashed password gets stored in the database but I would like to do it as a hidden variable. I am new to php and databases so please let me know if this has been answered before as I couldn't find the solution anywhere.

UserController.php

<?php
namespace App\Http\Controllers;

use App\User;

use Illuminate\Http\Request;
use Illuminate\Support\Facades\Hash;

class UserController extends Controller{

//List all the users
  public function index(){
    $users = User::all();
    return response()->json(['data' => $users], 200);
  }
//Store a new user
  public function store(Request $request){
    $this->validateRequest($request);

    $user = User::create([
      'email_id' => $request->get('email_id'),
      'first_name' => $request->get('firstName'),
      'last_name' => $request->get('lastName'),
      'username' => $request->get('userName'),
      'password' => Hash::make($request->get('password'))
      ]);

      return response()->json(['data' => "The user with id {$user->id} has been created"], 201);
  }

  public function show($id){
    $user = User::find($id);

    if(!$user){
      return respose()->json(['message' => "The user with {$id} doesn't exist"], 404);
    }

    return response()->json(['data' => $user], 200);
  }

  public function validateRequest(Request $request){
    $rules = [
      'email_id' => 'required|email|unique:users',
      'password' => 'required|min:6'
    ];
    $this->validate($request, $rules);
  }
}
?>

User.php

<?php

namespace App;

use Illuminate\Auth\Authenticatable;
use Laravel\Lumen\Auth\Authorizable;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Contracts\Auth\Authenticatable as AuthenticatableContract;
use Illuminate\Contracts\Auth\Access\Authorizable as AuthorizableContract;

class User extends Model implements AuthenticatableContract, AuthorizableContract
{
    use Authenticatable, Authorizable;

    protected $fillable = [
        'id', 'email_id', 'first_name', 'last_name', 'username'
    ];

    protected $hidden = [
        'created_at', 'updated_at', 'password'
    ];
}

?>