11 “The poor has been left unto You.” For therefore is he poor, that is, has despised all the temporal goods of this world, that You only may be his hope. “You will be a helper to the orphan,” that is, to him to whom his father this world, by whom he was born after the flesh, dies, and who can already say, “The world has been crucified unto me, and I unto the world.” For of such orphans God becomes the Father. The Lord teaches us in truth that His disciples do become orphans, to whom He says, “Call no man father on earth.” Of which He first Himself gave an example in saying, “Who is my mother, and who my brethren?” Whence some most mischievous heretics would assert that He had no mother; and they do not see that it follows from this, if they pay attention to these words, that neither had His disciples fathers. For as He said, “Who is my mother?” so He taught them, when He said, “Call no man your father on earth.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)