The Son said-I am your offspring. The Shruti declare that one's offspring is called Putra, because one is rescued by him. One's own self, again, takes birth as his son. Do you, therefore, rescue yourself by your own self.
पुत्र उवाच अपत्यमस्मि ते पुंसस्त्राणात् पुत्र इति स्मृतः। आत्मा पुत्रः स्मृतस्तस्मात् बाह्यात्मानमिहात्मना॥