public function userUpdate()
{
    if(Input::get('send')) {
        $arr = [
            'email' => Input::get('email')
        ];
        DB::table(Config::get('users_table'))->find(Input::get('userId'))->update(['is_active' => TRUE]);
        return redirect()->route('users');
    }
}

id bigserial NOT NULL,
username text,
email text,
permission integer NOT NULL,
is_staff boolean NOT NULL DEFAULT false,
is_active boolean NOT NULL DEFAULT false,
updated_at timestamp without time zone,
created_at timestamp without time zone,
remember_token text

Route::post('/user/update', [
    'as' => 'userUpdate', 'uses' => 'UserController@userUpdate'
]);

{!! Form::open(['route' => 'userUpdate', 'method' => 'post']) !!}

<label>Username</label>
{!! Form::text('username', $user->username, ['class' => 'form-control readonly', 'readonly' => '']) !!}

<label>Email</label>
{!! Form::text('email', $user->email, ['class' => 'form-control']) !!}

<label>Permission</label>
{!! Form::text('permission', $user->permission, ['class' => 'form-control']) !!}

{!! Form::hidden('userId', $user->id) !!}
{!! Form::submit('Update User', ['class' => 'btn green', 'name' => 'send']) !!}
{!! Form::submit('Cancel', ['class' => 'btn black', 'name' => 'clear']) !!}
{!! Form::close() !!}

public function userUpdate()
{
if(Input::get('send')) {
    $arr = [
        'email' => Input::get('email')
    ];
    DB::table(Config::get('users_table'))->where('id',Input::get('userId'))->update(['is_active' => TRUE]);
    return redirect()->route('users');
}
}

first() to limit(1)

$blog = DB::table('blogs')
        ->where('blogs.id', $id)
        ->first();

$blog = DB::table('blogs')
        ->where('blogs.id', $id)
        ->limit(1);