/usr/lib/ruby/2.1.0/ubygems.rb is in libruby2.1 2.1.5-2+deb8u3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 | # This file allows for the running of rubygems with a nice
# command line look-and-feel: ruby -rubygems foo.rb
#--
# Copyright 2006 by Chad Fowler, Rich Kilmer, Jim Weirich and others.
# All rights reserved.
# See LICENSE.txt for permissions.
#++
require 'rubygems'
|