Custom validation rules

I want to create a validation to a form that resets the password.

I have a method that checks whether the new password are the same and have more than 6 characters.

I miss only one thing to check if given the previous password is consistent.

    /**
* Reset user password
*
* @return void
*/
public function reset_password(Request $request){

    $this->validate($request, [
        'old_password' => 'required',
        'password' => 'required|min:6|confirmed'
    ]);

    $user = Auth::user();
    $user->password = bcrypt($request->password);
    $user->save();


    return redirect('/user/profile');
}

via chmod