Seeing that he owns absolutely nothing to ‘repay’....

“ Seeing that he owns absolutely nothing to ‘repay’ his debt, ‘his own consciousness’ of the fact ‘that he is himself the very substance’ of debt, so must he ‘repay’ with himself, so must he ‘return’ himself to Him Who owns him absolutely. ”

Syed Muhammad Naquib al-Attas

From : Islam: The Concept of Religion and The Foundation of Ethics and Morality